Problem fitting 700c tyre to new Smart Pie 4 rear wheel

[PhotoG090]

I am in the UK and have recently purchased the Smart Pie 4-700c rear wheel conversion kit. My problem is I cannot find a tyre that will fit over the rim. The wheel seems to have a rim that is deeper than the one on a standard wheel making it over size. I have tried two bike shops and a specialist e-bike shop and none of the mechanics have managed to fit a 700c tyre or come up with a solution. I have contacted Golden Motor dealers in the UK and come up against a wall of disinterest and/or lack of knowledge. Does anyone know if this could be a manufacturing fault or is there a tyre out there not commonly used on UK bikes that will fit this wheel. As a way around I am considering removing the hub and fitting it to a standard wheel rim. As a novice in this area I would be grateful for any practical advice.

[Bikemad]

Hi andto the forum.

I have a 700C Smart Pie 4 and the bike's original 700-38C tyre (which I believe has an inside diameter of 622mm) fitted onto the new rim without any problem.

From what you have said, I suspect you may have a 28" rim (700B) instead of a 700C, as some of the 28" tyres have a slightly larger inside diameter.
A 28" x 1 ½" (700 x 38B) tyre has an inside diameter of 635mm.

I have not been able to find anyone selling a 28" x 1 3/8"(700 x 35A) but these supposedly have an even larger inside diameter of 642mm!

This might account for why the 700C tyre does not want to fit.

You can easily compare the circumference of the old and new wheel rims by marking a line on the side of the rim and place this line on a line marked on the ground. Then roll the wheel one complete turn in a straight line along the ground and mark another line where the line marked on the rim touches the ground, then measure the distance between the two lines.
Do the same test with the other rim and see how much difference there is between the two rims.

If the difference is ~40mm then it must be a 28" rim instead of a 700C.

Before ordering a tyre to fit a 28" rim you should make sure that there will be enough clearance for the larger diameter tyre inside the frame (and possibly mudguards?) and also that your brakes have enough adjustment to move the pads ~6.5mm further from the axle to allow them to still line up with the rim (if you don't have disc brakes).

An alternative option would be top replace the rim, but this would also require new spokes of the correct length to suit the new rim.

If your wheel was ordered correctly but has been incorrectly supplied, you could simply return it for a refund, but I suspect the return shipping costs might be a bit expensive.

Under the circumstances, it would not be unreasonable to ask your supplier to send you the correct 700C rim and a set of matching spokes at their expense if it was definitely their mistake and not yours.

Alan
 

[PhotoG090]

  Alan, Thank you. At last someone who knows what they are talking about and takes the time to communicate. You are spot on with your assessment. The wheel supplied is indeed 28"and not the 700c. Now I understand the problem it's onward and upwards. You put the UK dealers and bike mechs in the shade. Once again thank you. Regards, Bob.

[PhotoG090]

Hi again Alan, I have failed miserably to find a tyre that will fit SMP4 700C wheel. Yes, the SMP4 wheel diameter is 40mm more than my 700. However we have tried 700C, 28" and even a 29" mountain bike tyre. None fit over the rim. I am being told that in the past the UK reduced the overall size of wheels. Could it be possible that Golden Motor are working to specification different from the UK? I am attaching an image that shows the SMP4 wheel next to a 700 from my bike. The circumference of the SMP4 rim outer edge measures 80" or 203cm. The 700 measures 78 3/4" or 200cm. Although the SMP4 is larger I am confident it fits the bike, I just need to source the correct tyre. Anyone got any ideas? Regards, Bob.

[Bikemad]

Bob, you need to understand that the rim you have is not a 700C rim and most 28" and all 29" tyres have the same internal diameter as a 700C tyre so they will not fit on your particular rim.

If you look at the following list of 28" Tyre information copied from schwalbetires.com you will see that the majority of these 28" tyres have a 622mm inside diameter, but the ones that should fit your rim are 635mm (shown in bold below)

18-622   28 x 3/4   700 x 18C
19-622       700 x 19C
20-622   28 x 3/4   700 x 20C
22-622   28 x 7/8   700 x 22C
23-622   28 x 7/8   700 x 23C
25-622   28 x 1.00, 1 1/16   700 x 25C
30-622   28 x 1.20   700 x 28C
28-622   28 x 1 5/8 x 1 1/8   700 x 30C
32-622   28 x 15/8 x 11/4   700 x 32C 700C COURSE
35-622   28 x 15/8 x 13/8   700 x 35C
37-622   28 x 1 5/8 x 1 3/8   700 x 35C
40-622   28 x 1.50, 28 x 1 5/8 x 1 1/2   700 x 38C
42-622   28 x 1.60   700 x 40C
44-622   28 x 1.625   700 x 42C
47-622   28 x 1.75   700 x 45C
50-622   28 x 1.90, 28 x 2.00   
60-622   28 x 2.35   
32-635   28 x 1 1/2 x 1 1/8   770 x 28B 700 x 28B 770B COURSE
40-635   28 x 1 1/2,  28 x 1 1/2 x 1 3/8   700 x 38B 700 x 35B 700 Standard 700B Standard
44-635   28 x 15/8 x 11/2   700 x 40/42B
28-642   28 x 1 3/8 x 1 1/8   700 x 28A
37-642   28 x 1 3/8   700 x 35A

If you place a straight edge on the top of your new rim it should produce a gap of ~13mm between the straight edge and the rim of your old wheel when placed side by side as shown in your photo.
If the difference is as much as 20mm it might even be a 700A rim which would require a tyre with a 642mm internal diameter, and I couldn't find any of those!

From what you have said, I suspect you may have a 28" rim (700B) instead of a 700C, as some of the 28" tyres have a slightly larger inside diameter.
A 28" x 1 ½" (700 x 38B) tyre has an inside diameter of 635mm.

There are very few tyres that are likely to fit your 28" rim, but I think the 700 x 38B tyre in the above link should fit your wheel and was the cheapest I could find (£12.60 including £2.99 delivery) but the supplier (Acycles) is located in France.

The only suitable tyres I could find quickly on the net in the UK were at SJS Cycles and the cheapest of these is £16.99 including £5.00 delivery:


           £27.99                           £24.99                              £11.99             
Click for more details

I can't explain why the postage cost is 67% higher to have it delivered within the UK than it is to come across from France.

Anyway, I hope this has helped you to understand why you "failed miserably to find a tyre that will fit".
Contrary to what you might have logically expected, a 29" tyre is not necessarily larger than a 28" tyre!

Alan
 

[PhotoG090]

Thanks again Alan. With your help I am starting to get some understanding of tyre/wheel measurement. Your research on suppliers is invaluable and I will post again when I have a successful resolution to this problem. Regards, Bob.

[Hastings]

I had the same problem I bought a 28/ 635 mm  by mistake. There was no way it was going to fit my frame.
The problem was solved by  purchasing a new 700C  /622 mm rim with matching spokes and change. Two good dealers are Gm Canada and Miromax. Can you return the wheel ?

[PhotoG090]

Well my 700C rim now has a 'lovely' yellow Schwalbe Delta Cruiser 700x38B tyre. It would seem that Golden Motor have indeed created a wheel to an old, almost obsolete 700B size. I consider myself lucky to find one, pity it had to be yellow but beggars can't be choosers. One other point, the tyre when fitted to my 700C bike just misses the bottom edge of the mudguard by millimetres. This is a big wheel compared to the 700C. Thank you everyone for your advice I hope my experience will be useful to anyone contemplating purchasing the SMP4 conversion kit.