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CB750K Alloy rims

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MarkCR750:
I think it's mainly cosmetics Phil , as Greebo said it may turn in a bit slower with a 19 but if you're not racing who cares, I put 18's on mine cos that's what the original CR had (at least I think it did!) but where do you stop?, for example the sliders should be magnesium and not have mudguard mountings adjacent to the axle but I'm definitely not going to the expense of doing that! 👀 , without getting a real CR frame nobody has a perfect replica (the headstock is lower) and the last time I saw a CR frame sold it was 8k and that was a few year ago.
PS you don't need a speedo for your MOT so don't worry about the gearing, you can always mark up your rev counter with 30, 50, 70 notches in top, not sure if the police will be impressed with that but that's what they're getting from me 😀.

Chris400F:

--- Quote from: philward on February 13, 2016, 12:02:32 PM ---I may be looking too deep at this but have been looking at Avon tyre catalogue which gives all widths, revs per mile, etc. http://www.avonmoto.com/download/Avon_mc_databook.pdf

--- End quote ---
I wish I could understand this tyre sizing malarkey, and I wish the manufacturers would be consistent in their recommendations.

If I go to the Avon Motorcycle Tyres web page (http://www.avon-tyres.co.uk/motorcycle) and tell it I have a 1977 Honda CB400/4 it tells me I need the following tyres:
Front: Avon RoadRider 90/90-18 51V
Rear: Avon RoadRider 100/90-18 56V
This is what I have fitted, and all seems well.

But .... If I look in the referenced Avon Tyre Catalogue this tells me that a 90/90-18 tyre should be fitted to a rim of width 1.85 - 2.50 (400 is 1.60), and a 100/90-18 tyre should be fitted to a rim of width 2.15 - 2.75 (400 is 1.85).

So Phil may be understandably confused, as I am. Can anyone else make sense of this?

Greebo:

--- Quote from: philward on February 13, 2016, 12:02:32 PM ---Hi guys
I may be looking too deep at this but have been looking at Avon tyre catalogue which gives all widths, revs per mile, etc. http://www.avonmoto.com/download/Avon_mc_databook.pdf
Questions
1) As I'm still waiting for 18 inch 2.15 rim to come into stock - as revs per mile is cocked up using a 18 inch rim (speedo), if I use 19 inch with 3.25 section ( seems skinny? - as recommended by Avon) - is handling any better/worse for 'not on the edge road riding'? Or is it about cosmetics (CR used 18s I think)
2) Should I just go for 4.00 on back to save cocking up gearing? Or slightly wider 130/80? Same question as above.

Anybody any experience of using above on road comments appreciated. Sorry to drag this out but going to be spending 500 squid and want to get it right!

Thanks again
Phil

--- End quote ---

Just going off topic, but still concerning the front end & handling.
The thing I tried to improve on when building me cafe racer was the stock fork brace which is not really up to the job,[ especially on uneven road surfaces ], an engineer freind tried making me a stronger brace for the stock forks, but because the brace has to be attached to the "fork risers" & also act as a front mudguard bracket he found that there would not be enough clearance, Also I did not want to get rid of the mudguard just to accommodate the stronger brace.  I even tried searching the internet to try & find if any of the 750 sohc specialised companies had come up with one, but I could not find one any where, so in the end I had to stick with the stock brace which is OK, but not good enough for those who want to push the front end hard through the twisties.... :o

K2-K6:
I was over at the Ace Cafe last week and looking around the bikes there was a nicely detailed Harley flat track replica parked there with 18 inch front and rear alloy rims laced to the hubs, it was the rims that first attracted my attention as the just looked very well made so I had a read of them to find they were produced by MORAD of Spain, a type I've not seen before.

Had a search around and they seem to make quite a variety of sizes and rim profiles, maybe of use as a supply.

Think much of the past race bikes used 18inch front as many of their tyres were supplied in that size from 60s onward.

K2-K6:
This maybe  helpful also, if you search "tachoma world tyre size calculator" and enter your sizes it'll calculate all the specs for you to see a direct comparison.

It is a US site for Toyota trucks but the calc sheet works fine for bike sizes as far as I've checked.

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