300-4 Tire - first impressions

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300-4 Tire - first impressions

Postby expresso » 19 Feb 2018, 22:39

I finally got to ride the chair with the new tire size 300-4 - chair looks nice - feels good over sidewalk cracks etc, - 10 PSI - i can manage it - i get the wheel shake at times - depends on surface - few other factors - - But making this change has changed how the chair handles feels - CG -

I may end up going back to 280/250 tire - a bit disappointed but at least now i know - if anyone is thinking of upgrading to this tire size - i would factor in how much you weight also - since that can have a Pos or Neg. effect - at least with the Kenda tire i am using - it needs more weight on the front tires to keep them firmly planted - tires are strong even at 10 PSI - dosnt look flat at all - seems full -

i am glad i tried it and it does fit - but i may end up taking them off - and going back - - its the speed that affects it more - at 8 mph - much better all around to handle - going faster - seems too soft and can bounce on certain types of bumps etc, - it may have raised the front end a bit which makes the chair more tipsy -

programming needs to be toned down - to smooth it out -

it has some Neg. effects that maybe may not be worth the trouble - if you are a heavy weight user - it may offer more Pos. results -

:|
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Re: 300-4 Tire - first impressions

Postby Burgerman » 20 Feb 2018, 00:22

I finally got to ride the chair with the new tire size 300-4 - chair looks nice - feels good over sidewalk cracks etc, - 10 PSI - i can manage it - i get the wheel shake at times - depends on surface - few other factors - - But making this change has changed how the chair handles feels - CG


Your whole chair is now too high. By which I mean CG is too high. Thats what causes the shake. CG is high because of lighter battery, taller tyres both ends.
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Re: 300-4 Tire - first impressions

Postby expresso » 20 Feb 2018, 01:05

thats right - thats the issue - but it just became more pronounced with the front tires now -

i can try to adjust programming so it dosnt take off too fast or stop too fast - to try to smooth it out during use - but i may just end up going back to the smaller tires and use them on the fork hole higher up which will lower the front a bit -

i managed ok with the 280 tires last summer - i was expecting just a better overall with the 300- tires - i was wrong

they are on and i will try to use them at least for a while if i manage to adjust settings enough - or else off they go - and back to smaller tire -

if i can find those tires you told me - 120-70 which would make it close to the original size for the rear also - i would get those tires now and put them on my spare rims ready to install once these go bad - may take a few years though - they seem very strong -

the fronts look cool - and are good if not going too fast - -

i cant seem to find those duro tires 120-70 size here in the states -
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Re: 300-4 Tire - first impressions

Postby snaker » 20 Feb 2018, 01:50

I deeply understand the trouble that the caster shake causes :cussing
Once it happens, it should be stopped ASAP :fencing

But 10inch casters offer very stable and smooth rides, especially when moving up short ramps or curbs. I do not want to get back to 8inch. I remember that we tried many ways. Some had good effects with my old square casters but all failed with the round Kenda. Eventually we took the Shirley's advice, tightening the bearings to prevent casters from swinging too freely. Actually, they only swing 1/4 turn if slammed and the shake almost disappears. My chair seems high CG, it has a stupid gap about 4cm under the seat for nothing. If I could lower the seat down that 4cm, the shake might no longer be a problem. A simpler solution is to eat more fast foods as BM's advice :mrgreen:

Slam the caster hard and it should stop in a half turn or three quarters.
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Re: 300-4 Tire - first impressions

Postby expresso » 20 Feb 2018, 02:21

My forks Castors are fine - they are tighten correctly - i changed all the bearings etc, there nothing else to be done to the castors - forks -

these tires are huge compared to the ones i replaced - which are not 8 inch tires - i had the 8 inch on the suspension forks when new -

i went to the larger forks fixed and it allowed me to use the larger 9 x 3 tire which is 280/250-4 that worked fine last year after some tuning with the PSI -

the reason i am having this issue is i changed my rear tires which were larger overall - it wasnt my objective to get larger tires - i just wanted black and wider on the same rim - going from stock 300-8 to 350-8 raised my rear up about 2 inches -

then going to the larger tires 9 x 3 - is where it started - going 8 mph was fine - even now with the 300-4 its fine at 8 mph - in terms of the shake -
but other things still are a bit off in handling because of this 300-4 tire -

i used the 9 x 3 tire last summer and pretty much was fine - i just adjusted some settings - and i will see if that makes it easier to handled during use full speed - if it dosnt tame it enough that i get comfortable using it at full speed -

i will go back to 9 x 3 tire and thats that - i did about 12 mile today to test it and it did get a shake here and there but it was fine 90 % of the time so thats fine with me - it will depend on the surface - uneven - bumps or cracks - and if i wheelie - then the tires hit the ground again - it can happen then and its usually the left side all the time - same as before and on my other chair also -

just looking at the chair parked next to me now - it looks cool - rugged and looks ready to go - too bad i may have to change back - it was still fine before
look wise - i just wanted to see for myself if the 300-4 tire cleared my motors and how it was going to feel -

i learned that it can be done but being too high CG - dosnt feel as good to me at full speed - if my chair didnt have a seat lift etc, - it may be difference - it would have been lower CG -

all well - live and learn - thats what its all about - cheers
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Re: 300-4 Tire - first impressions

Postby shirley_hkg » 20 Feb 2018, 04:28

expresso wrote:My forks Castors are fine - they are tighten correctly - i changed all the bearings etc, there nothing else to be done to the castors - forks -

-

the reason i am having this issue is i changed my rear tires which were larger overall - it wasnt my objective to get larger tires - i just wanted black and wider on the same rim - going from stock 300-8 to 350-8 raised my rear up about 2 inches -

- cheers


That is totally WRONG , that changing to 3.50-8 rear tyre results in a 2" rise . Must be 0.5" in arithmetic .

There is at least ONE thing you could try , if my memory is correct .

Having seen the drawings of the caster assembly you posted , there is A TUBE , between the upper & lower bearings , that prevents over-tightening . No matter how hard you tighten the nut that no preload can be added .

Try to look into it , if you could ger rid of the tubing , so you are allowed to adjust the pre-load then . Good luck . cheers
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Re: 300-4 Tire - first impressions

Postby snaker » 20 Feb 2018, 07:53

That's right in my case, the thing between 2 bearings. My dad just ground it a little.
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Re: 300-4 Tire - first impressions

Postby Burgerman » 20 Feb 2018, 08:08

Thats there to stop you loading the bearings since it damages them easily. You can load them with a spring, since the load remains constant regardless of temperature, over tightening etc. And adding friction here is not adressing the cause its preventing a symptom.
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Re: 300-4 Tire - first impressions

Postby shirley_hkg » 20 Feb 2018, 08:44

Couldn't agree more , but we're desperate . :worship

Think carefully , if the spring washer were really adding a load to the bearings , with a tube in between ; OR it's just pressing the 2 inner rings of the bearings against the two ends of the tube .
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Re: 300-4 Tire - first impressions

Postby Burgerman » 20 Feb 2018, 11:41

In a well designed high rpm system, bearings are always loaded to prevent skidding. In a powerchair the weight does that for the bottom one. The top one isnt loaded much at all. That tube prevents it. But at our speed it doesent matter. The correct way to add damping is to add a friction washer that slides on the OUTER race edge and does not add the pressure of the nut to crush both bearings together...

In my little gas turbines the bearings OUTER race is free to slide in and out the housing at the engines rear, and is loaded with a very carefully measured spring. This loads both front/rear bearings. If you remove this spring, the 160,000 rpms destroys a bearing every run. If loaded correctly then they survive this speed very happily as long as they are lubricated with a light mist of kerosene and 2% oil. This cools, and doesent allow them to slip and develop flat spots. We dont have this need in a powerchair!
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Re: 300-4 Tire - first impressions

Postby expresso » 20 Feb 2018, 17:39

there is nothing on the forks to tighten any more than it is - i dont think it would benefit me at all -

when i changed the rear tires - i measured the battery box from the floor to the box - checking the ground clearance - i am pretty sure it was 2 inchs or very close to that in difference between the two tires - OD on the new tire was close to 15.5 or 16 inches - the stock tires were closer to 14 inches OD -
it was a difference i felt the moment i sat in the chair -

and i had to remove the smaller anti tip wheels from 3 inch in the rear because it was too small and i got stuck tipped back on a hill - where before with the stock tires and same 3 inch wheels - i was fine - i had to put back the 4 inch stock wheels and i still have more clearance than i had from stock wheels and 3 inch anti tippers

from that moment i added those rear tires - it lifted the rear - i still had stock 8 inch front tires with suspension forks -

then i put the fixed forks for larger tires 280/250 - 4 and with lower PSI - about 14 PSI i had last year - it was 90% fine - managed to use it all summer - every now and then depending on surface etc, i get a shake but easy can manage it - i was pretty much fine -

now i just added the larger tires 300-4 and that was a huge difference also - in size wise - much larger OD than the 280 tire - even with low 10 PSI - the tire itself is strong - i like how it looks - and feels on flat ground etc, but in full speed use - it can be a bit too soft bouncy feelings and its a bit higher also -

it handled better with the 280 tire - i made a few changes to the settings to tone it down a bit - will be testing it tomorrow - along with my new camera -

if i feel i can deal with it - maybe i need to adjust to how it feels - i may leave them on - if not - i will change them back to 280 tire and its fine - if that happens - i will have a pair of tires for someone who wants them :)
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Re: 300-4 Tire - first impressions

Postby expresso » 20 Feb 2018, 17:43

besides the shake at speed at times - i can deal with it since its not bad - the main issue here now is about the tire size itself - lifted the front more and changed how it handles in the process - the shake is not even there at 8 mph speeds - it shows up now and then when going full speed closer to 10 mph

front end feels light since i am not a heavy person - think of a car with soft tires - too soft suspension - and higher CG - compared to a lower CG and stiffer tires etc, wont bounce as much and handle better - thats how i am comparing it -

but there were some POS. effects also - just more NEG. ones than POS -

tomorrow i will have a better idea if its something i can deal with or just swap them back -
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Re: 300-4 Tire - first impressions

Postby expresso » 24 Feb 2018, 01:09

i am going to measure the clearance - changing to these tires lifted it up alot compared to stock -
this is the real reason i am having front caster shake issues - - if the rear tire was kept same OD - those 300-4 tires may have been fine in terms of shake - but either way - not needed for me - too large - too soft feeling and i am not that heavy - so 280-250 tire is the best size for me and this chair -

will be changing them back next week -
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Re: 300-4 Tire - first impressions

Postby rustyjames » 24 Feb 2018, 01:23

Expresso, when you had the 300-4's mounted, what did you do so they wouldn't rub the footplates? That's assuming you're running the typical ones.
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Re: 300-4 Tire - first impressions

Postby expresso » 24 Feb 2018, 17:19

rustyjames wrote:Expresso, when you had the 300-4's mounted, what did you do so they wouldn't rub the footplates? That's assuming you're running the typical ones.


i still have them on right now - will be changing them next week - turns out on this chair 646se - they cleared them - i didnt do anything to them - on my P222se chair - it didnt clear them -

the foot rests are in a different position on the seating frame on the 646se chair with the motion seating system - they can be adjusted also - only out or in - a bit - if i recall when i got this chair new - they did bring them out a inch more i believe -


i measured my clearance in the rear - its close to 5 inches from the floor to the battery box -

do you have the same chair with the stock tires ? if you do - can you measure what your clearance is - if i am not mistaken its about 3 1/2 inches with stock tires -
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Re: 300-4 Tire - first impressions

Postby rustyjames » 24 Feb 2018, 23:51

@ Expresso, that's right, I forgot you had a different seating system on your 646. I'm building a 646 with 300-4 tires and there's no way I'll be able to use the standard hangars/foot plates, I'll have to come up with some kind of custom design. I'll try and get you that measurement, if I could do it while sitting in my chair I'd give it to you right now cheers but I'll have to do it when I get over my shop and measure from it from a spare.
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Re: 300-4 Tire - first impressions

Postby expresso » 25 Feb 2018, 01:02

No problem rusty - no rush - i am just curious - what the difference is in clearance - my P222se was stock seating with just tilt - and the 300-4 tires didnt fit there - they hit my foot rests -

but the 646 is just the frame stock from sunrise - then they added motion concepts seating - and the spot where you hang the foot rests - they can be adjusted a bit forward more to give clearance - i guess when i got the chair - they must have been close and they adjusted it from day one this way -

its about an inch forward more - - i bet once i put back the 280 -250 tires - i could move it back and still clear them - i may try that once i am settled with the tire size i am going to keep on it -

300-4 - dosnt work for me riding - -etc, too big a tire - lifts the front end too much - - dosnt feel right - but if a heavy user sits on it - it may be Ok

i am about 165 lbs - either way i think 280 - is a better fit for my chair with CG - if i went back to stock rear tires - it would lower it more and be even better overall - but i plan to keep the rear tires at least till they wear out - i hope maybe i can find a nice rear tire thats as wide but lower OD like the stock size

i dont find them here - as BM says - Duro - or the other brand - 120/70 or 110/80 - stock would be a 90/90 i think for a 300-8 - i like the 350-8 but its a bit taller OD -

at this point - i dont care for that extra speed if its going to cause issues - i dont mind going back to smaller OD - but want to keep the width now -
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Re: 300-4 Tire - first impressions

Postby shirley_hkg » 25 Feb 2018, 04:04

The absorber is adjustable on rear height , itsn't it ?
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Re: 300-4 Tire - first impressions

Postby rustyjames » 25 Feb 2018, 15:01

@ Shirley, that adjustment is to change the dampening effect, won't change the height.
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Re: 300-4 Tire - first impressions

Postby expresso » 25 Feb 2018, 17:02

rustyjames wrote:@ Shirley, that adjustment is to change the dampening effect, won't change the height.



thats correct- - i have adjusted mines last time with the tech. when i was trying to figure out the front caster shake - i get confused what does what with that spring - we made a few turns on the spring and one turn on the Red. knob there - i forget what each one does - rebound and damping etc,
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Re: 300-4 Tire - first impressions

Postby Burgerman » 25 Feb 2018, 18:54

Thers a large ring nut that sets preload, Large ring. Its threaded, and can be turned. Tightening towards the spring increases pre load and chairs height. Slackening it reduces preload and lowers chair.
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Re: 300-4 Tire - first impressions

Postby expresso » 25 Feb 2018, 20:44

Burgerman wrote:Thers a large ring nut that sets preload, Large ring. Its threaded, and can be turned. Tightening towards the spring increases pre load and chairs height. Slackening it reduces preload and lowers chair.



yes we reduced the preload - to lengthen the spring loosen it - the red knob we turned also just one turn inward i believe - the spring was turned outward about 6 turns i think they were half turns so about 3 full turns on the spring
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Re: 300-4 Tire - first impressions

Postby Burgerman » 25 Feb 2018, 20:47

Unscrew it about 10 or 15 full turns. You "sit" on the spring. By unscrewing that nut, by maybe 1 inch you lose about 1 inch of height.
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Re: 300-4 Tire - first impressions

Postby expresso » 25 Feb 2018, 21:14

Burgerman wrote:Unscrew it about 10 or 15 full turns. You "sit" on the spring. By unscrewing that nut, by maybe 1 inch you lose about 1 inch of height.


what effect would it have if i did loosen the spring more and turning the nut inward again ?

from what i recall after the changes we made - it kinda of felt as if the frame was given more slack - sort of making it longer the front end in contact more i believe the feeling i remembered -
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Re: 300-4 Tire - first impressions

Postby rustyjames » 25 Feb 2018, 23:51

I gave Shirley and others incorrect information. Yes, those shocks could be adjusted to increase the height, but I don't think you could gain anything more than 1" though because the motor housing doesn't have that much travel before bottoming out. To tell you the truth, I don't think the shocks on these chairs really do much at all to absorb any harshness, to me the ride is rigid with no suspension effect at all.
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Re: 300-4 Tire - first impressions

Postby Burgerman » 26 Feb 2018, 01:13

and turning the nut inward again ?


What nut? A small one? Probably damping. Leave alone...
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Re: 300-4 Tire - first impressions

Postby expresso » 26 Feb 2018, 01:20

rustyjames wrote:I gave Shirley and others incorrect information. Yes, those shocks could be adjusted to increase the height, but I don't think you could gain anything more than 1" though because the motor housing doesn't have that much travel before bottoming out. To tell you the truth, I don't think the shocks on these chairs really do much at all to absorb any harshness, to me the ride is rigid with no suspension effect at all.



not sure how it would increase the height - maybe in the front of the chair ? now on the other hand it feel they work pretty good the shocks etc,

But it could also be in my case - my seat is tilted a bit all the time so its not all the way down in a flat zero position - being that its tilted - the seating does absorb which acts like a shock that can be in my case and in your case - if you ride with the seat all the way down flat zero -

you may feel the bumps more - you should try adjusting those shocks - turning the Nut also to soften it ?

i can tell you this - if you go to tubes - tires - that would help alot - my chair came with suspension forks and smaller 8 inch foam tires - and they felt Ok also but once going to the larger fix forks with Tubes - was alot better even -
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Re: 300-4 Tire - first impressions

Postby snaker » 26 Feb 2018, 01:33

Burgerman wrote:Thers a large ring nut that sets preload, Large ring. Its threaded, and can be turned. Tightening towards the spring increases pre load and chairs height. Slackening it reduces preload and lowers chair.

Mine locate at the rear and have the same effect. I mean tightening increases height, slackening reduces it. But it is strange that slackening causes more caster shake, tightening reduces it.

And like expresso, these springs have good effect in shock absorbing. If tightening too much, I feel sitting is very hard.
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Re: 300-4 Tire - first impressions

Postby shirley_hkg » 26 Feb 2018, 02:45

Burgerman wrote:
and turning the nut inward again ?


What nut? A small one? Probably damping. Leave alone...


Yes, the small nut at front is a fluid valve , for damping (how fast the rebounce die). drunk2
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Re: 300-4 Tire - first impressions

Postby expresso » 06 Mar 2018, 01:59

back to 280 size tire in the front - dosnt look bad - will have to test soon - hopefully this weekend

this time i used the other slot on the fork - brings it down a bit lower - with 12 PSI - will see how it feels both handling and if any castor shake
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