Topic: Biggest Rear tire for 73 CB750

[Vincent P]

Hello all,

Need to replace the rear tire on the back of my 73 CB750.

What is the widest and if possible lowest profile I can put on without the risk of it interfering with anything i.e. swing arm, chain, brake linkages?

[70CB750]

Better stick to original size for handling.

[Vincent P]

How much do you think a wider lower tire would affect the handling???

Compared to other bikes I've had in the past, 83 Kawasaki LTD, 83 Honda Nighthawk, 83 Honda CB1000; these all handled much better in the turns 

[70CB750]

I don't know enough to tell, but from reading the forum, that's the conclusion I made for myself.

Handling is affected by head bearings and the swingarm bushings.  Tighten it there if you didnt already.  Also there are areas of the frame where you could add a gusset to stiffen it up - Hondaman says, I would have to look in the book for that.

Tires - there is something about the front and back profile that should match - but hopefully somebody will weight in. 

Your bike and your butt, do what you want by all means - and I am not being smart a$$ or sarcastic here, but tire dimension choice should not be mainly how much space is there in the swingarm.

[Bankerdanny]

The stock wheels on the SOHC4's are pretty narrow, so going much wider than stock doesn't really help much.

But this subject has been discussed many times. if you use the search box in the upper right corner you should be able to get the answers you are looking for.

[Xnavylfr]

That's pretty good ! He ASKED how much wider . In a stock swingarm , the WIDEST you can SQUEEZE in is a 140/90. Anything is possible if you were to MODIFY!!!


Xnavylfr(CHUCK)

[crazypj]

Putting a140 on stock rim is just dumb.
It doesn't get wide, it just gets taller as beads are squeezed then wears the center out even faster
I've done it, but, only because I was broke and picked up a brand new Dunlop for $45.00
It was completely bald in the center in less than 2,000 miles
If I'd had the $100.00+ for correct tyre I would never have done it (in fact, I've always changed wheel rims for wider ones if I wanted to fit wider tyres)

[750K]

Comfortably I'd say a 130, although it wears flat in the center. Had a 130 on my 77, I switched to a 120 rear last year and am way happier. The bike rolls in and out of turns much smoother, the front and rear work together entering and exiting a turn when they are closer in width. From what I gather the usable contact patch of the 130 is the same as the 120, you just get longer life and a better handling bike with the 120. I did like the look of the 130 but I'd rather have a better handling bike than a wider looking rear tire.

[PeWe]

I decided for 100/90-19 front and 120/90-18 rear after reading a good thread on this forum.
http://forums.sohc4.net/index.php?topic=19346.25

Both wheels and tires must match for good handling. There are some charts with rim vs tire with resulting angles.

Metzeler tires after my own good experiences many years ago with a grip matching the bike and rainy days as sunny, this time Lasertec.

[Vincent P]

Comfortably I'd say a 130, although it wears flat in the center. Had a 130 on my 77, I switched to a 120 rear last year and am way happier. The bike rolls in and out of turns much smoother, the front and rear work together entering and exiting a turn when they are closer in width. From what I gather the usable contact patch of the 130 is the same as the 120, you just get longer life and a better handling bike with the 120. I did like the look of the 130 but I'd rather have a better handling bike than a wider looking rear tire.

This is exactly what I was after. My reasoning for a lower wider was to get more contact surface on the ground, but some of the other comments make sense; thanks CrazyPJ as always. I have logged quite a few miles in this past month, just over 2000, and plan on doing extensive rides for next season.

It would be nice to have it sit a bit lower (I'm only 5'.6") which would feel better when at a stand still for me, but I can accomplish this with the new shocks and seat to be put on soon.

So the next real decision on my part is which brand....

[Black 750K8]

Comfortably I'd say a 130, although it wears flat in the center. Had a 130 on my 77, I switched to a 120 rear last year and am way happier. The bike rolls in and out of turns much smoother, the front and rear work together entering and exiting a turn when they are closer in width. From what I gather the usable contact patch of the 130 is the same as the 120, you just get longer life and a better handling bike with the 120. I did like the look of the 130 but I'd rather have a better handling bike than a wider looking rear tire.

+20 Same here had a 130 went to 120 and will never go back. Not with a stock wheel.

[Black 750K8]

Comfortably I'd say a 130, although it wears flat in the center. Had a 130 on my 77, I switched to a 120 rear last year and am way happier. The bike rolls in and out of turns much smoother, the front and rear work together entering and exiting a turn when they are closer in width. From what I gather the usable contact patch of the 130 is the same as the 120, you just get longer life and a better handling bike with the 120. I did like the look of the 130 but I'd rather have a better handling bike than a wider looking rear tire.

This is exactly what I was after. My reasoning for a lower wider was to get more contact surface on the ground, but some of the other comments make sense; thanks CrazyPJ as always. I have logged quite a few miles in this past month, just over 2000, and plan on doing extensive rides for next season.

It would be nice to have it sit a bit lower (I'm only 5'.6") which would feel better when at a stand still for me, but I can accomplish this with the new shocks and seat to be put on soon.

So the next real decision on my part is which brand....

Same here I am going with the lowering kit from cycleX 2" shorter tubes and shorter shocks.

[70CB750]

Comfortably I'd say a 130, although it wears flat in the center. Had a 130 on my 77, I switched to a 120 rear last year and am way happier. The bike rolls in and out of turns much smoother, the front and rear work together entering and exiting a turn when they are closer in width. From what I gather the usable contact patch of the 130 is the same as the 120, you just get longer life and a better handling bike with the 120. I did like the look of the 130 but I'd rather have a better handling bike than a wider looking rear tire.

This is exactly what I was after. My reasoning for a lower wider was to get more contact surface on the ground, but some of the other comments make sense; thanks CrazyPJ as always. I have logged quite a few miles in this past month, just over 2000, and plan on doing extensive rides for next season.

It would be nice to have it sit a bit lower (I'm only 5'.6") which would feel better when at a stand still for me, but I can accomplish this with the new shocks and seat to be put on soon.

So the next real decision on my part is which brand....

I have lowering brackets you can have for postage.

[Vincent P]

Thanks 750, message me.

[Retro Rocket]

That's pretty good ! He ASKED how much wider . In a stock swingarm , the WIDEST you can SQUEEZE in is a 140/90. Anything is possible if you were to MODIFY!!!


Xnavylfr(CHUCK)

Chuck, you can go wider than that, 160 even, you need far bigger rims but thats not the point, the stock rim is made to suit a 110, that is the correct size tire and going wider on a stock rim is well PJ said it best...

Here's a 160 slick on a 4.5 inch x 17 rim on a stock swingarm, tight but it fits...

[Dimitri13]

You will definitely have a wider contact patch with the widest tire you can fit... after you square it off and absolutely destroy any of the handling it may have had with the tire.

Stick to stock sizes or get a wider rim for a wider tire.

[Xnavylfr]

RR , thanks for the picture it say's loads,  Where's the ENGINE AND CHAIN???
I have a DOHC swingarm which sets the wheel back 3 inches and running a 16x3" laced to the HONDA hub with the short cush drive. My wheel sits centered and a 140 is perfect, 1/2" from chain to tire sidewall. I could POSSIBLY run a 150 but it would be TIGHT. You can offset the rim to the right and get more room(if it is spoked) but then you get back to MODS. 



Xnavylfr(CHUCK)

[DORIGTT]

Tires get square if your riding style is droning along on the highway correct?

What made the CR750's handle the wider tires then?  If I recall reading, they ran a ~ 110 front and 135 rear on wider than stock wheels.

[Retro Rocket]

Tires get square if your riding style is droning along on the highway correct?

What made the CR750's handle the wider tires then?  If I recall reading, they ran a ~ 110 front and 135 rear on wider than stock wheels.

Wider tires are fine with wider rims, the point you missed is that tires are made for specific size rims, wrong tire on the wrong rim and you'll have problems in more than one area...  You should see our post classic racing now we are allowed to use modern wheels, mainly to give access to better tires.. They handle better than their original set up BUT, there's a lot more to it than using different size rims, the triple clamp offset and rake and swingarm length all come into consideration when you start changing rim sizes, especially changing diameter, something that simply looks good doesn't always work...

RR , thanks for the picture it say's loads,  Where's the ENGINE AND CHAIN???
 
Xnavylfr(CHUCK)

Whats your point, That wheels fit, its that simple, needed to machine a little off the sprocket carrier and use an offset front sprocket to get the chain line right, but they fit, even the same axle size. I don't do things in halves Chuck, you should know that by now....   As a matter of interest, those wheels are going on a F1 750/4..., 3.5x17 front and 4.5x17 rear....

[Vincent P]

My two main criteria for the original post, and why I said the widest I could go was as I stated more contact surface; and lower because of wanting the bike to sit lower to fit my frame.

I would give up a wider tire for handling in a heart beat, and in the end lowering the bike via shocks or a seat, or perhaps a proper lowering kit is preferred.

Thanks for all the input all.

[Xnavylfr]

RR= My point was , It WASN'T as easy as just bolting on the WIDE rim and TIRE and taking off. Modification had to be done to make it work on a stock frame. I know what has to be done to run wider wheel assy., Did it on a KZ1000.

Vincent P= To get closer to the ground, you can change shocks to shorter but stiffer and also have your seat refoamed and covered. An auto upholstery shop can install denser foam and lower the seat area, which can give you 1 -2" closer to the ground.

Xnavylfr(CHUCK)

[crazypj]

Use a 120 but lowest profile you can find (probably 120/80?)
It may only get you 1/4" but every little helps
You can cut seat foam and replace cover so it looks more or less stock, slice an inch or so off the bottom so you don't have to re-shape the top surface

[Vincent P]

Thanks Crazy; will talk to my local shop and see what he can get me.

[Black 750K8]

The stock wheels on the SOHC4's are pretty narrow, so going much wider than stock doesn't really help much.

But this subject has been discussed many times. if you use the search box in the upper right corner you should be able to get the answers you are looking for.

Did you mean upper left?

[crazypj]

left for custom search