CB750K Alloy rims

[philward]

Thanks Chris - pub beckons and will have a look when I get back
Cheers

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[MarkCR750]

Any recommendations for tyre sizes for 2.15 x 18 front and 2.50 x 18 rims?

There is a table on page 7 of this document which may give some guidelines.
http://www.maxxis.co.uk/media/65556/2013-Motorcycle-Tyre-Catalogue.pdf

Probably best to have them professionally done Phil, central wheels did mine, they had to do a different spoke pattern to accommodate the angle of the nipple holes, or so they said, I can't see anything different myself (see photo above) anyway they only charged there normal rate, when they rang me it sounded at first as though they wouldn't be able to use the rims, but I could hear one of them in the background say he could do it, anyway if your builder thinks there's a problem show him the photo of mine.

[philward]

Thanks again Mark - I compared your pics to my std wheels (and your back wheel spoke sizes are 30mm smaller than std) and I can see that spoke angle is steeper. What size and make of tyres have you got on your bike?

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[MarkCR750]

They are Avon road runners Phil, I will check the sizes tomorrow.

[philward]

Just looking at same and guessing at  90/90 and 120/90 will accommodate slightly wider rims

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[Chris400F]

Any recommendations for tyre sizes for 2.15 x 18 front and 2.50 x 18 rims?

There is a table on page 7 of this document which may give some guidelines.
http://www.maxxis.co.uk/media/65556/2013-Motorcycle-Tyre-Catalogue.pdf

I recall that I posted this link once before and someone pointed out that the tyres it recommended for the 400 are narrower than those other makers recommend.
Standard front rim is 1.6, rear is 1.85, recommended tyre sizes from the document are 80/90 front and 90/90 rear.
I use Avon RoadRiders, they recommend 90/90 front and 100/90 rear.
So maybe worth seeing whether other sources say the same, 90/90 may be a bit narrow on the front.

[MarkCR750]

Phil I have a 130/80V 18 66v on the rear and a 90/90 18 51v on the front, they are Avon road riders, I said road runners before by mistake.

[philward]

Thanks Mark

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[philward]

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

[Greebo]

Mines got stock size Avon roadriders fitted 19"F 18"R wheel, I have no complaints at all.

The only thing I would say about the 19" Front Wheel is you will find that the bike drifts wide slightly coming out of corners, but its not a big deal,& because this Café racer build cost me an arm & a leg I respect it a bit more than if it was a cheapo street cafe racer.

in other words I don't want to drop it..  

[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]

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

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]

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

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....

[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.