Tyre size on my GSX 750 E - 1981

[Guest]

Im doing some modifications on my GSX750, and the first ting that I really need to change is the tyre size. I bought a new tyre this spring, but it looks like a moped with the original size.

Can I go for a 160 tyre? Has anyone tried?

[Nessism]

Assuming your bike uses the same 2.15" wide wheel as most other GS750's, the widest tire matching that wheel is a 120. You might want to look at the side of the wheel for the molded lettering and confirm the size just to be sure.

[phrode]

Original size is 130

[hampshirehog]

Original size in 'old money' is 4.00 X 18. This equates to a 120/90 X 18. My 750 likes that size on the back best - ok it looks skinny but it works just fine.

[Nessism]

4.00" x 25.4 mm/in = 101.6 mm

A 120 is really pushing the limit as far as a 2.15" wheel goes. One thing though, it's possible that Suzuki used a 17" wheel in Norway (or where ever the bike came from). The 17" rear is 2.5" wide so you could use a 130 tire if that is the case. In either case, no way to use a 160 unless you did a wheel swap.

[hampshirehog]

4.00" x 25.4 mm/in = 101.6 mm

Does it work like that Ed? I've never understood tyre sizes properly and I just get the tyre size conversions off:

http://www.conti-bike.co.uk/default.asp?pid=26

The 120/90 is the 'right' size tyre comparing like with like. The 130 'upgrade' is quite common but all it seems to do is just make the wheel look fatter - I've not noticed any improvement in handling.

[Steve]

Does it work like that Ed? I've never understood tyre sizes properly and I just get the tyre size conversions off:

http://www.conti-bike.co.uk/default.asp?pid=26

The 120/90 is the 'right' size tyre comparing like with like. The 130 'upgrade' is quite common but all it seems to do is just make the wheel look fatter - I've not noticed any improvement in handling.

They have changed the way they label the tires over the years, so there is a bit of confusion. While the strict mathematical equivalent of a 4.00 tire is 101.6 mm, the actual cross-section of a 4.00 tire was actually just a little bit over 4.00 inches. Not sure if it amounted to the 18.4 mm difference, but the overall size and weight ratings of today's 120 tires are called for. I believe that the 120 width in the tire size is the actual width, across the widest part of the tire, while mounted on the recommended size rim.

I will have to check, but I am not sure that the 17" wheel is a 2.50. I know the 16" wheels on the L models is, but I am not sure about the 17s.

.

[Nessism]

Yes, the 17" wheel IS 2.5".

No, the modern 120 does not equal an old 4.00, it's more like a 110 (I disagree with that generic table published by Continental). I agree that it is wider than a 100 (not sure why I posted that).

I have a 120 on my 1000S, with 2.15" wide wheel, and frankly, the tire hangs over the edge of the rim more than I'd like to see. One of my old bikes had a 4.00 tire on it and it was noticably more narrow than the 120.

[mrbill5491]

Stay as close to factory specs on the tires. That bike was design for those tires, anything else bigger and it will adversely affect your handling, It did mine and I went back to mostly stock sizes and no problems.

[Nessism]

Stay as close to factory specs on the tires. That bike was design for those tires, anything else bigger and it will adversely affect your handling, It did mine and I went back to mostly stock sizes and no problems.

There is nothing wrong with increasing tire sizes, but you should not exceed the limits of the wheels.

[phrode]

I see... What about a new rim? Is there any other type of rims that can fit my bike without modifications?

[mrbill5491]

There is nothing wrong with increasing tire sizes, but you should not exceed the limits of the wheels.

Pretty much what I meant, next time I will state that about the wheels/rims. When I went bigger tires that is exactly what happened, I exceeded the limit of my rims and screwed my handling all to hell.

[gearhead13]

You can use a 2.5" wheel off of an 1100 or go bigger with a 3.5" off an 1150.
I have the 1100 aluminum swingarm with a 3.5" 1150 wheel and mounted a 150/70/17 on it. Just the brake stay has to be modded to clear.

[phrode]

The 1100 and the 1150, is it a specific year?

[gearhead13]

I think all the 1100E's came with 2.5" and the early 1150 was 3.0" the later ones were 3.5"
All 17" rims, the 750E's I believe all had 18x2.15