Topic: CB750 K7 Newbie Wheels Question

[drpoyser]

Hey all,

I recently bought a CB750K7 (my first bike) and am in the process of restoring it.
There is a replacement (David Silver) 19" rim on the front however the rear looks pretty shot.

It seems to be the standard 17" size but I understand it can be difficult finding decent tyres for this.

My question is if I am to lace a new rim, what recommendations would any of you chaps have from similar experience.

Cheers. 

[Geeto67]

If you are rebuilding your wheel I would go with an 18" diameter rear. I would also recommend you go with an alloy rim.

[Wobbly]

It seems to be the standard 17" size but I understand it can be difficult finding decent tyres for this.

That is simply not true. There is a wide variety of tires you can use. I use the Battlax BT-45 myself, but there is a wide range available. Approved sizes (approved by Honda, for those who have to pass inspections) for the K7 are 100/90 x 19 front, 130/90 x 17 rear.

[Wobbly]

Here is a small selection:
http://www.sbm-honda.motorrad-daten.de/index.php?mo_hersteller_id=18&ccm=&motorrad_id=284&mode=suchergebnis&lastmode=suche&catID=mc&searchmode=search_mc

[Black 750K8]

I also went with the Battlax BT45 rear 17" but the 120. My old tire was a 130 but it wore to square on the sides and would fall on the edge when leaning hard and I didn't like that feeling. But it was not a battlax. This wheel is almost to small for a 130 but it will fit.

[750K]

I'm running Avon road riders and had no trouble finding an appropriate size for the 17" stock rear, 120-90-17's. I find that size much nicer than the 130 I had on there prior, which were Bridgestone spitfires. They're a nice tire as well, 130 was just too wide for the stock rim and wore flat by the end of its life.

[Wobbly]

I'm running Avon road riders and had no trouble finding an appropriate size for the 17" stock rear, 120-90-17's. I find that size much nicer than the 130 I had on there prior, which were Bridgestone spitfires. They're a nice tire as well, 130 was just too wide for the stock rim and wore flat by the end of its life.

Nicer or not--the appropriate size it is not. Both, Honda and Avon, only permit the 130 size. http://www.avonreifen.com/sites/default/files/CB%20750%20K7%20CB750K_0.pdf

[750K]

Haha, I don't give a #$%* what Honda permits. Stock metric size is narrower than 120 iirc so it doesn't really matter does it.

[lucky]

You can get Avon Roadrider 26's for your bike.
The front will be bi-directional and the rear will be one direction only. Same tread design.
Go to the AVON website to get the tire number, then order from who ever has the best price for you.

If you can get a set of 17 inch alloy wheels from a CB750
automatic model you will save 12 lbs.

[Wobbly]

Haha, I don't give a #$%* what Honda permits. Stock metric size is narrower than 120 iirc so it doesn't really matter does it.

That's great for you. But it does matter to those who have to pass inspection, and don't want to drive without being insured anymore (me being stationed overseas, for instance). One might also wonder why neither Honda nor any (!) tire manufacturer supports that size for the K7 if it doesn't make any difference. I understand that, back in the States, you can fit a bicycle wheel if you like. But I wouldn't call it the appropriate size--and neither does Honda.

[750K]

Just because "they" recommend a 130 width rear for the stock rim doesn't make it the best tire for the bike, 130 is pushing the limit of what fits on the stock 17" rim. The usable contact patch ends up being the same between the 120 & 130 series and you don't end up with a corner when the flat spot starts to wear in. The 120 rear is closer matched to the 100-90-19 front and the difference is noticeable entering and exiting a turn. I'm glad we don't have the same anal retentive rules in Canada, no do we have to do an annual inspection to pass safety. That must really suck balls...

Just because one manufacturer or the other says it appropriate doesn't mean it is, I've run both sizes and can tell you a 120-90-17 is a way better fit. 

[lucky]

Just because "they" recommend a 130 width rear for the stock rim doesn't make it the best tire for the bike, 130 is pushing the limit of what fits on the stock 17" rim. The usable contact patch ends up being the same between the 120 & 130 series and you don't end up with a corner when the flat spot starts to wear in. The 120 rear is closer matched to the 100-90-19 front and the difference is noticeable entering and exiting a turn. I'm glad we don't have the same anal retentive rules in Canada, no do we have to do an annual inspection to pass safety. That must really suck balls...

Just because one manufacturer or the other says it appropriate doesn't mean it is, I've run both sizes and can tell you a 120-90-17 is a way better fit.

There are charts online that tell you what size rim is required for your tire width.

[750K]

I know Lucky, I'm not looking for new tires. I'm good, thanks lol.

[Stev-o]

I put a Dunlop 404  130/90-17 on my K8 cuz I like fat tires.  It never squared off while I had it and it's sold and gone!

[drpoyser]

Great, thanks for all the advise folks. This is really helpfully stuff. Out of interest if I were to go with a 18" at the rear. Would the front also need to become 18" or stay at 19"?

[Geeto67]

It is preferable to go to an 18" front but not necessary. 19" front, 18" rear were the cb750 sizes from 1969-1976 on the k bikes and 1975-1978 on the F model. I don't know why Honda dropped to a 17" in 1977 on the k bike (76 on the automatic), but I suspect it was not a performance reason as all the sporting Honda models stayed 19" front, 18" rear. 19"/18" is the most common vintage size so finding tires is pretty easy.

Most modern bikes use 17" rims so going to wider rim than stock in 17" in the rear opens you up to modern sport rubber but I doubt you'll find a match for the 19" front and would have to convert to 17" there as well. I don't have a lot of info on 17" wheels on a cb750 so I don't know if that is going to cause the bike to become twitchy.