Rear Rim sizes

[Cabmkr]

Can anyone tell me how different width rear rims effects handling? I assume a narrower rim would make the bike turn better with a bit less straight up traction and a wider one would hook up better in a straght line but turn a little harder. Tire size being the same in both cases. The bike in question is a 78 IT400 with 79 yz250 rear shock and swingarm and 38 mm forks from a 81 YZ125

 Chris

[colmoody]

Thats a good question Chris. Personally I have no idea and doubt if you would get a definitive on that one but would be good to read a few opinions all the same.

[LWC82PE]

Well it depends on what tyre is used with what rim but if you were to use the same size tyre on 2 different rims you would get this

wide rim -  more tread contact, lower ride height at rear, slower steering
narrow rim - less tread contact, higher ride height at rear, quicker steering

[Nathan S]

I look at like this:
Tyre size is determined by engine power (too big and you'll bog the motor, too small and you lack traction).
Rim width is determinted by tyre size.

There's plenty more to it (as LWC's post suggests), particularly if you start talking about the finer points of handling, but you won't go too far wrong using that rule of thumb.

Personally, I reckon 110 or larger tyre = 2.15" wide rim. On a 1.85" rim, the larger tyres are balloon shaped and tend to feel underinflated all the time.

[jimg1au]

NATHAN
some yamaha wheels in the pre80 era have 2.50 wide rims i have 2.
also sc500a had a 2.50 wide rim while the 360/250 had the 2.15

[Nathan S]

Yeah. In my experience, most of them have corroded into uselessness by now...  120+ tyres on them, IMHO.                                     

[EML]

Interesting what LWC says about tall profile tyres speeding up the steering. This happens alot on dirttrack when trials tyres are fitted to mxers and then they get real twitchy-just when you dont want them to be and then guys start lengthening swingarms and lowering forks through the triples etc... etc......