KR-1S.co.uk Forum

I already have an RGV250P swingarm and RS250 wheel (4.5 inch) in my KR, however, I was wondering if it was possible to fit a 5.5 inch rear rim or is this too big??

I think if you fit the RGV wheel it gives you a better choice of rubber
i dont think ppl go any larger for there road bikes.. the racers might be different tho.
Worth checking the team sparrow link on the main page

i wouldnt have thought it neccersary to go any bigger than 4.5 inch, that should take a 150/160 section tyre. any bigger is just for looking at and i think it would look a bit silly.
there must be a technical reason why racers dont use huge rear tyres, maybe it effects the turn in speed for corners or something like that but i'm guessing.

I used to have a 5.5 inch rim on my TZ and used 150 section tyres.
The only reason I mention it is because I may be able to get hold of a 5.5 inch magnesium racing wheel that should be a little lighter than the standard RS250 wheel I already have in there.
...It was just a thought

The SM tyres that we use for racing are a 160 profile. A standard 160 will fit a 4.5" rim without any problems however the SM are recommended to be used with a 5" rim. I proved that by running off the edge of the front tyre at Snetterton and I still had a 4mm wide chicken line on the rear. MJ uses a 5" dymag rear and his rear tyre profile is a lot better.

Also I think that a 5" rim is the maximum you can fit into a KR. Plus you will need to put a kink into the rear brake brace or it will rub on the edge of the tyre when it gets warm. Personnaly I will be getting a 5" rim wheel made up sometime.

As Elf says I use a 5" as that is the minimum I think you can get away with on a 160. Any less and the tyre pinches and you end up with less contact patch.

In a KR swinging arm 5.25" is about the biggest I have seen.

In a Suzuki arm 5.5" should be ok. Chain run will be close also as Elf says I have put a curve in the torque arm to clear the tyre.