Help with tyres

[faico_26]

Hello!
Greetings from Spain. I’m Fran and I’m modifying an Invacare Mirage to make it look cooler.
Usually I use the common known grey solid rear tyres 12 1/2 x 2 1/4 (62-203) but I just received a pair of black solid tyres which are 12 1/2 x 2 1/4 (57-203). I tried to find the differences between these 2 sizes (57 or 62) but I didn’t get a clear answer. In theory 57 should mean 57mm outer tyre diameter and 62 would refer to 62mm, is it? But both tyres are 2 1/4 which also refer to tyre width.
I found in many bikes websites that 57-203 is 12 1/2 x 2 1/4 R. Does anyone what R means?
Finally I have another question: how can I know the right tyre size to fit the inner rim width? My wheelchair shop told me that knowing the tyre size is not enough because a too narrow tyre would get loose in a too wide inner rim width. For example, she told I can’t use the invacare Bora tyres (12 1/2 x 2 1/4) because my Mirage’s rims have too wide inner rim diameter.
Thanks!!
Fran

[Burgerman]

Where to start.

Rims. Are in inches. Typically stated as for e.. 8 x 3 or in the motorcycle or car world 8 x 3J and thats the same thing. The 3 part is the rim width where the tyre sits. Half an inch either way does not stop you fitting a TUBE or TUBELESS type air filled tyre. But is a big issue if you are sing those horrid foam filled or polyurethane filed tyres.

Your 12 1/2 x 2 1/4 is the tyre size. What is lacking is the rim measurement. So it should read 12.5 (12 1/2) x 2.25 (2 1/4) x 4 or 6 or 8 which is the rim diameter. Tyres are what is called NOMINAL sizes. That means that if you buy 6 similar sized tyres from different manufacturers they will all vary in external size slightly. But will all fit the rim exactly. That means when you measure them they will not be what you expect. Your MM measurements like (57-203) show that. And its a small difference that make no difference to your usage. In this case the 57 is width. 203 is diameter. 5MM either way will be unnoticeable. R means radial ply.

[faico_26]

Hello,
Thanks for the reply. I find this issue a bit confusing for my limited knowledge if tyres and rims. Just to understand it, if I want to order a pair of rear tyres for my wheelchair, what I should look to be sure they fit my rims? I know that I should look for 12.5 (12 1/2) x 2.25 (2 1/4) but the rim diameter never appears on eBay or other shops. I’m using solid tyres (at least they are black).
I would like to use tubeless tyres which look so cool and sportive, like Kenda, Dunlop or similar. I refer to black tyres with white letters and nice thread like these: https://www.bicycletechbar.com/products ... duty-black
But I can’t know if these tyres would fit my rims, can I?

[Burgerman]

You are talking about solid or polyurethane filled tyres? If so its very hard to know.

They are often made to fit several different rim widths. Even where every tyre marking/size is the same. For eg, Some 8 inch diameter rims, are 1.5, 1.75, 2, 2.25, 2.5 and all found on powerchairs. And the tyre is filled to match the rim. So you would need to ask what size (width) rim the tyre is designed to fit. Then measure your own. If they are tube type, or tubeless, they will fit all rim sizes. You will not find tubeless on a powerchair though, unless you fit different rims as I do.

THIS tyre https://www.bicycletechbar.com/products ... duty-black

fits an 8 inch rim. But we cannot know the width without asking. The tyre size does not tell us. It tells us that it is:

12.5 INCH overall diameter. And that its 2.25 wide/deep. (2 1/4) Thats TOP and BOTTOM.
So that means it is 12.5 inches diameter, LESS 2.25 top, and 2.25 bottom (so 4.5 inches of tyre) leaving an 8 inch rim...

[faico_26]

Exactly, that is the point: I’m using solid polyurethane tyres, “wheelchair” tyres (which I know you hate them)
Therefore my wheelchair shop was right. They told the same as you did. It’s about the bed width. Ok now I got it.
From your experience, in my case, do you think I could find rims to be able to use tubeless tyres. The diameter should be 12,5 and would not like to get the wheelchair go wider to the 57cms I have now, so the tyres should be 62mm or less wide. Do you think I could find a suitable combination of rim+tyre??
Many thanks from Barcelona!!
Fran

[Burgerman]

Can you fabricate an adapter or a means to fit a different rim? Or this size is likely the closest tube tyre option. But it may need a wider rim ideally but will actually fit... https://www.lifelightmobility.co.uk/70- ... RAA532.htm Its 1.6 inches tall...

Exact replacement grey and black https://www.lifelightmobility.co.uk/2.5 ... RAA162.htm

Will be 12 diameter but needs wider rim... https://www.lifelightmobility.co.uk/80+ ... RAA552.htm

Correct diameter but needs a wider rim again... https://www.lifelightmobility.co.uk/90- ... RAA491.htm

If so theres many. But forget 12.5 and look at a little bigger or/and wider. Like:
viewtopic.php?f=2&t=6997#p126878 here... All are mine.

[ex-Gooserider]

Are you sure on the ISO number interpretations? I know that in bicycle tires (and manual chairs) the ISO size numbers refer to the RIM bead seat diameter and the tire cross section size... (<Rim Diameter> - <section diameter>)

I.e a 26 x FRACTIONAL inch (i.e 26 x 1 3/8) size (typical on most adult manual chairs) will be an ISO 540-??? while a 26 x DECIMAL inch (i.e. 26 x 1.375) size will be an ISO 508-??? as the rim diameters are different... On rims, the ISO number format is the same but gives the bead seat diameter

I haven't checked, but I think the same numbering applies to M/C tires as well, and given that it's an ISO standard, I would expect it to apply to all tires and rims (with possible extra numbers if there is a big difference in the section height and width?)

If the same thing applies to smaller power chair size tires, I'd expect that the two sizes in Falco's original question would be referring to different rim diameters, not outer tire diameters - so the two sizes would NOT interchange!

62mm ~ 2.44" or possibly a 2.5" nominal rim size? while 57mm ~2.24" or possibly a nominal 2.25" rim... That seems sort of small unless the Mirage is a FWD or MWD chair, in which case it's reasonable for caster wheels?

Hello!
Greetings from Spain. I’m Fran and I’m modifying an Invacare Mirage to make it look cooler.
Usually I use the common known grey solid rear tyres 12 1/2 x 2 1/4 (62-203) but I just received a pair of black solid tyres which are 12 1/2 x 2 1/4 (57-203). I tried to find the differences between these 2 sizes (57 or 62) but I didn’t get a clear answer. In theory 57 should mean 57mm outer tyre diameter and 62 would refer to 62mm, is it? But both tyres are 2 1/4 which also refer to tyre width.

ex-Gooserider

Where to start.

Rims. Are in inches. Typically stated as for e.. 8 x 3 or in the motorcycle or car world 8 x 3J and thats the same thing. The 3 part is the rim width where the tyre sits. Half an inch either way does not stop you fitting a TUBE or TUBELESS type air filled tyre. But is a big issue if you are sing those horrid foam filled or polyurethane filed tyres.

Your 12 1/2 x 2 1/4 is the tyre size. What is lacking is the rim measurement. So it should read 12.5 (12 1/2) x 2.25 (2 1/4) x 4 or 6 or 8 which is the rim diameter. Tyres are what is called NOMINAL sizes. That means that if you buy 6 similar sized tyres from different manufacturers they will all vary in external size slightly. But will all fit the rim exactly. That means when you measure them they will not be what you expect. Your MM measurements like (57-203) show that. And its a small difference that make no difference to your usage. In this case the 57 is width. 203 is diameter. 5MM either way will be unnoticeable. R means radial ply.

[ex-Gooserider]

I should learn not to work from memory when pontificating....

I just went back to the definitive source on all things pedal bike - Sheldon Brown's site... - specifically

https://www.sheldonbrown.com/tire-sizing.html

I got the numbers backwards!!!! First set of numbers is the section, second is the bead diameter.... From Sheldon's chart -

12 1/2 x anything - 203 mm Juvenile, scooters

I don't know where Falco got his measurements from, but what he gave was an ISO style format, which at least on pedal bikes is much nicer to work with than the inch sizes...

As I noted, the inch sizes are easily confused as there are several different 'standards' that use similar numbers but won't interchange...

But on ISO, you just need to make sure the rim and tire both have the same SECOND value (i.e ??? - 540 on most manual chairs). The first number gives the width between the bead seats on a rim, or the inflated width (diameter) on the tire, so you need to make sure the ISO rim width is less than the ISO tire section size - Again per Sheldon:

A general guideline is that the tire width should be between 1.45/2.0 x the inner rim width.

If you pull the beads apart and measure the total width from bead to bead, it should be approximately 2.5 x the ISO width.

So assuming they are ISO numbers, Falco's tires are both 12.5" bead diameter, and thus are probably interchangeable, depending on his rim width. Given that there is only a 5mm difference, less than 1/4" between the two, I doubt it would be a problem...

=============

However the plot somewhat thickens... I just checked the wheels I got from Shirley since they were easy to lay hands on...

The nominal 3.50-8 tires are Yuanxing brand - and have a number under the nominal size YX-P192-02.
The two different nominal 2.50-4 tires are either Cheng Shing with a number C-202-16 or a Kenda with number K-351-006 on them

None of the numbers make sense as ISO formats - they look more like a part number with a prefix that specifies the manufacturer.... So it looks like they don't do ISO number sizes in the tire sizes that we use more often on power chairs...

ex-Gooserider

[faico_26]

Hi everyone!
Thanks again for the help. Basically I was looking for a pair of cool black tyres in the style of those slick tyres Burgerman put on the green wheelchair. But obviously keeping the size my wheelchair can fit. For what I’ve learnt I should look for 62-203 or 57-203. I just stopped looking for solid polyurethane tyres. I have 2 of these in black. Look normal, better that grey for sure, but not cool.
I could fabricate some adapter but I but like to keep the rim as it is. So I’m thinking on buying tube tyres. I know it is risky but it’s my only option to find a pair of black nice tyres. Since they would be tube tyres, bed width is not so critical as with solid tyres, isn’t it?
What do you think about this one? https://rover.ebay.com/rover/0/0/0?mpre ... 2470125755

[Burgerman]

The reason they look good is because they are wide, and low profile to keep the same diameter.

So you WILL need wider rims.

[faico_26]

Now I’m looking for 62-203. That is 62mm outer tyre width and 203 rim diameter. 12,5 inches should guarantee that it is the outer tyre diameter I need.
Please have a look at this slick tyres. They look great: https://quickact.de/5/Reifen/Rubena-Mit ... i-Reifen-für-den-Slalomkurs,-Größe-12,5Zoll

Many thanks
Faico

[Burgerman]

Those are fragile. They should fit.

Do you understand that 203mm is the rim diameter?
And 203mm is really just the metric equivalent of a standard 8 inch rim as fitted to scooters and most powerchairs?

So ANY tyre that ends in 8 will fit?

So 250 x 8. 2.75 x 8, 3.00x 8? etc. And that each one is say 3.00 x2 plus8 = diameter? And that diameter isnt critical. So up to an inch bigger will be OK.

So you can search for:
75 x 8 or 80 x 8 or 70 x 8 or 65 x 8 tyres as a metric size too?

E.G. this will fit. https://www.lifelightmobility.co.uk/70- ... rettyPhoto

[faico_26]

Thanks Burgerman, I’m learning a lot about tires and rims, but it’s rather complicated because there are several different size systems.
I found a web which explains about it: https://www.motorbiketireshop.com/biker ... -explained
When I say I want the tyre to be 12,5 inches diameter and not higher is because I don’t want the chair to get higher. The same with the width of the tyres: I don’t want them to be wider than the standard 62mm because that would increase the overall width of the chair (currently 57cms).
I keep on searching for tyres! I’ll keep you informed of my research results.
Kind regards,
Faico

[faico_26]

Hi,
I recover this old topic to check if tubeless tyres would be an option for my new Q300R.
The chair has seat lift so it’s quite heavy.
The chair now has solid tyres (8” front, 12 1/2” back) and it’s so bumpy, well I don’t know if bumpy is the correct word in English to describe that I feel everything of the ground in my body. If the ground is not super flat I feel everything and I even feel numbness in legs.
My Invacare Mirage has also solid tyres and no suspension and it is super smooth. I don’t know why I feel everything so harsh with the Q300R. Maybe is it because the chair is much heavier than the Mirage?
I have been looking for tubeless tyres but I cannot find anything online.
Any advice?
Many thanks,
Faico

[Burgerman]

Tubeless tyres need tubeless rims.
So that means they are one part, have a special ridge to seat the tyres securely, etc. And I think finding a tyre that narrow that is tubeless will be impossible.
One of the reasons the ride is harsh is solid tyres... The other is that the chair has very little suspension travel. And small wheels and no front suspension.

You really need bigger tyres with a larger cross setion so that you need less pressure to support the weight. Thats why I fit wider rims, fatter tyres to all my chairs as the spasm I suffer cannot stand the skinny tyres or "flat free" solid ones its literally painfull! Dont know how anyone can run those.

But you have no front suspension and rock hard solid small casters too. So punished at both ends.

[faico_26]

Tubeless tyres need tubeless rims.
So that means they are one part, have a special ridge to seat the tyres securely, etc. And I think finding a tyre that narrow that is tubeless will be impossible.
One of the reasons the ride is harsh is solid tyres... The other is that the chair has very little suspension travel. And small wheels and no front suspension.

You really need bigger tyres with a larger cross setion so that you need less pressure to support the weight. Thats why I fit wider rims, fatter tyres to all my chairs as the spasm I suffer cannot stand the skinny tyres or "flat free" solid ones its literally painfull! Dont know how anyone can run those.

But you have no front suspension and rock hard solid small casters too. So punished at both ends.

So my current rims would NOT allow me to install tubeless tyres, that’s a pity.
Any idea why my Invacare Mirage also with solid tyres is much more smoother? It has no suspension at all but it is much lighter than the Q300R.

[Burgerman]

Non at all. Makes no logical sense. Weight shouldnt make a difference.

[Burgerman]

A tubeless tyre has no tube (obviously!) and so the RIM itself is designed to be airtight. So its normally a single part. Like the one near my PC below.

It has two "raised bumps" that the tyre bead jumps over as its inflated. The tyre is a very tight fit onto the rim. It has a soft mooth rubber bead on the tyre. The tyre inside has an airtight "tube" type rubber bonded and vulcanised to its inside.

The air is sealed inside and no tube. That also a very strong and tough tyre. These are basically motorcycle tyres designed for speed. Much higher quality than the usual tyres fitted to a chair. And the rims are cheap! at around £12 each. The tyres are £50 each!

And worth it.

[Burgerman]

Heres a pic of my bench.

Left... And middle.
2x 120/70-8 Diro Kitaco tubeless tyres.
2x 3.5J x 8 inch tubeless alloy wheel rims awaiting tyre fitting... Look CAREFULLY at the rims you can just see the "bump" that tubeless rims must have. Near the beads.

On the right...
8x 230Ah (244Ah actual) LiFePO4 from Amy Zheng!

This is a basic kit needed to convert any half decent but simple powerchair from a "pram" to a real powerchair... That has 100 mile range and fatterbetter stronger tubeless tyres that are more comfortable!

But you wont want the added 3 inches of width. I dont care because thats still the same width as across the arms. So narrower tyres wouldnt help in a doorway for e.g. In other words they dont actually make my chair wider.

[Burgerman]

These chairs are 25.3 inches wide. And 25.6 wide.
And full sized GRP 24 battery area.

[Raro]

Estas sillas miden 64,5 cm de ancho y 65,7 cm de alto

65.7 centimeters tall?

[Burgerman]

Wide. Total chair width.

[Burgerman]

All these are tubeless too!

[Burgerman]

And not one has a stock wheel...

[Burgerman]

These are tubeless, and going on a Dietz chair!

[Raro]

By the way, you said those rims weren't for that ten, right?

[Burgerman]

I still cant decide! I have got plans to buy a used one that isnt NHS and fit them to that chair. Ideally 6mph, lithium etc. And no lift. Watching eBay... And using that NHS chair only for dirty jobs, at home etc. Its too slow!

The point is that I am trying to show that tubeless is much better but needs non stock rims. And if going to the bother of doing that then wider, larger cross section is better for lower pressure, stronger tyres, better ride comfort. And tubeless because: Solid flat free give an awful harsh ride. And because tubes suck, and punctures ar problematic. Think balloon...

So adapters are required. Rims are cheap, good tyres are not!

[Burgerman]

It is possible to fit the same tyres to stock non tubeless rims. And use a tube. But you must make the wheel rims wider. One way or another. You still benefit from stronger bigger tyres but have a tube...

The Q700 had 2 part rims. I added a 3rd part. to make the rims wider. It is an extra bead rim from some Sunrise Jive wheels. With the lip (edge) cut off. So it adds an extra inch in the middle.

See martin my carer sat in it here:

[Burgerman]

Or his brushless one, widened with sheet metal and rivets!

Where theres a will theres a way... Even on brushless hub motors.

This was a 4 inch wide rim. Up from 1.75...

And a 110/80-8 tyres. With TUBE!!! I never give up!

[Burgerman]

I took a couple of pics to show whay a tubeless rim is tubeless.

And to show the rims I use, and the adapters that shirley made for these rims. To fit the Dietz chair in this case.

Rims are solid alloy, electroplated, tubeless 3.5J (width between beads) x 8 inches diameter. Meant for honda monkeybikes, X50 etc.
These rims come in many sizes.
Tyres are the DURO tubeless 120/70 - 8 size and not cheap! Superb quality.

Pic of the rim. NOTE the two raised bumps. Those keep the tyre in place and initial inflation causes the tyre to jump with a pop oer these. Needs a tyre fitting machine to remove them. Ignore the goo near the valve it is silicone grease. Aids in sealing and fitting the valve.

Heres a pair ready to fit on the bench. These have an as yet unpolished stainless centre disk. And this has a hole in it. That hole is for a bolt and load spread washer (same as the 4 already fitted) and it goes into the motor shaft. Its M8.

1.

2.

This is an adapter that shirley made to fit the Dietz chair. Its 20mm I think?

This is the tyre... (no shit sherlock)