Topic: Rim width recommendations?

[DaveL]

I just purchased a 1975 CB750F project bike with severely rusted wheels. I'm going to do a resto-custom sort of build on this bike as I need to retain the two-up seating. Anyway, I'm looking in to aluminum rims to lace up to my hubs and have some questions.

What size front and rear tires are good on these bikes for handling primarily and looks second? I'm thinking maybe 130/80 -18 on the rear and 100/90 -19 on the front? So the only source for aluminum wheels I can find is from Buchanan. Other than the 'crowning' and 'flattening' aspect of wider vs. narrower rims I don't know what the handling changes might be. I'm looking at a 3.5" wide rear rim and a 2.15" or 2.5" front - likely the 2.15".

Anyone with experience on these issues have constructive input for me?

Thanks,
Dave

[Bill/BentON Racing]

Dave 350x18 pretty wide,300x18 would also work(hard to find?)250x18 or 19 work fineup front,didn't Ks come with 185 f & 215 rear?Good Luck,Bill,What swingarm you using? 

[Tower]

Here is a chart I put together some time ago for this type of question...

[DaveL]

Dave 350x18 pretty wide,300x18 would also work(hard to find?)250x18 or 19 work fineup front,didn't Ks come with 185 f & 215 rear?Good Luck,Bill,What swingarm you using? 

I'm not sure what size the stock rims were as the stock rims I have are severely rusted and the stamp is no longer there. Right now with the stock '75 swingarm and 120/90 -18 tires I have about 3/4" each side between the tire and swingarm, so there's quite a bit of room. I may look in to putting the longer arm from the later bike on, or I may fab a swingarm if all else fails - though I want to keep the bike looking not too modded.

[MCRider]

I just purchased a 1975 CB750F project bike with severely rusted wheels. I'm going to do a resto-custom sort of build on this bike as I need to retain the two-up seating. Anyway, I'm looking in to aluminum rims to lace up to my hubs and have some questions.

What size front and rear tires are good on these bikes for handling primarily and looks second? I'm thinking maybe 130/80 -18 on the rear and 100/90 -19 on the front? So the only source for aluminum wheels I can find is from Buchanan. Other than the 'crowning' and 'flattening' aspect of wider vs. narrower rims I don't know what the handling changes might be. I'm looking at a 3.5" wide rear rim and a 2.15" or 2.5" front - likely the 2.15".

Anyone with experience on these issues have constructive input for me?

Thanks,
Dave

I've messed around with many wheel sizes. I have a 75 CB750F rolling chassis I bot from a guy who had Bucahanans make a 300-18 rear and a 2.50 18 front. These look very proportional and like that's what the bike should have had to begin with. Mine has a 130/80-18 on the rear and could stand a 140. It has a 110/80-18 on the front which looks great, proportional and functional. I'd drop kick that 19" front first thing.

My project bike has a 3.50/17 on the rear which is cool but a tad unecessary. I went 2.50/17 on the front.

The 18" are the best I think for ground clearance (you're riding 2 up?) and the 18" front will perk up the handling, turn in and braking.

My project with 17" may give me problems with side and center stand height (I'll have to shorten the stands) and scraping the muffler. I may regret it.

I think Bill has the stock widths correct and they are 2 skinney for the tires we are talking about.

PS: the 3.5 rear and the 2.15 front would be fine. I'd stay with a 18 on the rear for ground clearance. You could go to a 140, maybe a 150, but it may not clear the brake stay. Unless you're really upping the horsepower, a 130 is all you need.

I'd change the front to a 2.5/18 though.

[gane]

Dave. I'm w/ MCRIDER, I went with 2.15 18 / 3.50 18  sun rims from Buchanan's  @ 20 years ago.and run  100/90-18 and 130/90 18 w/no clearance  probs on my K6. tho If i were to do it again would go 2.15-17 and 3.50-17. simply for the avail. of current rubber. As an asside, Techniques and quality may have improved over the years, but colored anodized rims faded on my gold rims after 4 or 5 years. silver seems timeless. also, stainless spokes are still pristeen.luck G

[DaveL]

Thanks for all the feedback! I'm definitely leaning toward a 3.50" x 18 rear (I asked around about 18" tire availability vs. 17" tire availability and am not worried about that aspect) and am now considering the 18" front.

[lordmoonpie]

I've got a WM3 front and WM5 rear so I reckon that's 2.5" and 3.5" isn't it? All fits beautifully with rear wheel spacers from M3 but running dual calipers up front means the tyre doesn't clear the second caliper. That means a tortuous method of getting the wheel in by unboting calipers, wheel in without spindle, calipers on, discs on and then finally the spindle - about 40 minutes to take the wheel out of put it back in....

Have to sya the WM5 rear looks superb!

[Gamma]

Lordmoonpie, what make of rim are you using?

[lordmoonpie]

I think they are DID.....came from www.discovolantemoto.co.uk with nice stainless waisted spokes too 

[Tower]

Assuming you want the 3.5" rim on the back to allow you to put on the widest rubber without creating a large "pinch angle" and hence squirmy condition.
Now, consider tyre height to swingarm and fork constraints.

For example:
The standard CB750F swingarm has about 6.5" clearance where the rubber meats the arm.  So, it should accept 150/70 (5.9") or maybe even 160/70 (6.3")max rubber. 
On a 17" wheel that means heights of 25.3" and 25.8" respectively.
Anything taller or wider will probably not fit.

But, on an 18" wheel, that extra inch means the rubber is closer to the pivot and probably means anything taller or wider than 150/70-18  (5.9" x 25.3") will not fit. At least, not fit safely.

The shorter rim will therefore give you a bit more room for a wider tyre.

Next, consider how you want to match the rear wheel height to the front wheel.
The standard front wheel height is 25.6".  A tyre 120/80-18 is 4.7" x 25.6" tall and should fit between the forks, as well as match front-to-rear wheel height.  Anything wider or taller and the front end rubber might rub.

So, that means if you're keeping the stock swing arm and front trees, then your best widest fit is:
3.5" x 17" rear with 160/70-17 tyre (6.3" x 25.8")
2.5" x 18" front rim with 120/80-18 tyre (4.7" x 25.6")

[DaveL]

So, that means if you're keeping the stock swing arm and front trees, then your best widest fit is:
3.5" x 17" rear with 160/70-17 tyre (6.3" x 25.8")
2.5" x 18" front rim with 120/80-18 tyre (4.7" x 25.6")

Thanks for all the work! I'm pretty  much decided on a 3.5" x 18" rear with a 130/80 tire or (140) and a 2.5" x 18" front wheel with a 110 tire. I don't want to suck up whatever power the old bike has with too much rubber!

[Tower]

No problem, Dave.  That chart I posted is actually a calculator I developed a long while back - plug any values in and it shows the results and front-rear comparisons.  Here are the results of your choices of tyres and rims...

Front: 2.5"x18" rim with 110/90-18 tyres (4.33" x 25.8") 13.2o pinch angle (in the green zone) and reading on your OEM speedo will show 1% under actual speed.  I assume you meant /90 aspect tyres as /80 aspect will create too short a tyre height (24.9"), increase the pinch angle to 14.8o (now in the orange zone) and effect your speedo reading (it will show 4% - 5% over actual speed) .

Rear: 3.5"x18" rim with 130/80-18 tyre (5.12" x 26.2") 11.20o pinch angle (in the green zone).

Two observations come from these specs:
1) you will need to adjust the front/rear shocks to compensate for a slight understear that the tyre heights will create. (the bike will be a tad more steady at high speed, but a tad more difficult to turn)
2) The rims are to the wide side for the tyres selected, but well within a safety and handling margin that should give you great tyre performance.

[DaveL]

Nice! Thanks for the eval! Now to take the flame wrench to the spokes on the old wheels, hit the hubs with walnut or glass bead, anodize, and assemble with expensive rims!

[Bill/BentON Racing]

LMP,I think 300x18 is WM5.350x18 WM6.Li'l 590 race bike is 300x18 rear 250x18 front,great combo,running 140 on rear,110 up front,Bill

[seven]

Here is a chart I put together some time ago for this type of question...

Hey Tower, thanks for the Chart. Something like this should be pinned to the top of the wheels and tires section of FAQ. But I think you got the rims and tire sizes wrong for the K8. The stock front wheel should be a nineteen incher with a 3.50H-19 recommended tire size and rear rim should be fitted with a 4.50H-17A size tire.

I am going with an 18 inch rear rim on my K8 and I bought a DID 2.15 wide rim to replace the stock 17 inch rim. But I only realised after I bought it that the stock 17" rim is 2.50 wide. So now I'm looking for a wider 18 inch rim to suit (around 2.50-3.00). Might use the 2.15 x 18 rim on the front though.

Anyone out there know of any bikes on the forum that are running with an 18 inch front and rear wheel setup?

Cheers

[greasy j]

I have a K1 with stock swingarm, I used a 150 in the back on a 16" wheel and it works but there is no clearance. I wish I would have used a 140, but it makes no dif now.

I'm doing the same thing as you and gettin aluminum rims. ther is an .xml sheet on this page that a member made. just plug in the sizes and you get the results (download)

http://sites.google.com/site/alansdocuments/

I think I'm goin with 18's front and back. goin for functionality first, then looks. last time I did that backwards!

[greasy j]

No problem, Dave.  That chart I posted is actually a calculator I developed a long while back - plug any values in and it shows the results and front-rear comparisons.  Here are the results of your choices of tyres and rims...

Front: 2.5"x18" rim with 110/90-18 tyres (4.33" x 25.8") 13.2o pinch angle (in the green zone) and reading on your OEM speedo will show 1% under actual speed.  I assume you meant /90 aspect tyres as /80 aspect will create too short a tyre height (24.9"), increase the pinch angle to 14.8o (now in the orange zone) and effect your speedo reading (it will show 4% - 5% over actual speed) .

Rear: 3.5"x18" rim with 130/80-18 tyre (5.12" x 26.2") 11.20o pinch angle (in the green zone).

Two observations come from these specs:
1) you will need to adjust the front/rear shocks to compensate for a slight understear that the tyre heights will create. (the bike will be a tad more steady at high speed, but a tad more difficult to turn)
2) The rims are to the wide side for the tyres selected, but well within a safety and handling margin that should give you great tyre performance.

I know this is a little old, but I was wondering;

how about the 3.5"x18" rim with 130/80-18 (5.12" x 26.2") tyre in the rear
and the 2.5" x 18" front rim with 120/80-18 tyre (4.7" x 25.6") in the front.

is it not good to have the tires closer to the same size, (width)?

I am using a gl1000 front end so I believe I have a slightly wider clearance in front.

also the rim sizes are an inch different but the tires are almost the same size, would it be better to have a wider rim in front or narrower in back?

I know this topic has been beat to death, if you are sick of reading these tire size discussions ignore this thread and check this out instead:

http://www.peopleofwalmart.com/?paged=10

[Kevin400F]

The WalMart people thread was awesome.....

At the risk of keeping the original rim thread going, I always like to check the tire manufacturer's recommended rim width range for the tire I plan to use.  I don't always go by it, mind you, but I like to check it. 

an example:
http://www.avon-tyres.co.uk/motorcycle/roadrider

[Bill/BentON Racing]

Even with 2.50x18 up front be careful with 120 f tire width,I recommend 110/80/V18,it's whats on 590 race bike and IT WORKS.120 heavier,wider,clearance problems and turn in!,Bill

[greasy j]

Even with 2.50x18 up front be careful with 120 f tire width,I recommend 110/80/V18,it's whats on 590 race bike and IT WORKS.120 heavier,wider,clearance problems and turn in!,Bill

cool, thanks. I want whatever is going to work best.

so I'll go with the 110-90 front and 130-80 rear.

[greasy j]

The WalMart people thread was awesome.....

At the risk of keeping the original rim thread going, I always like to check the tire manufacturer's recommended rim width range for the tire I plan to use.  I don't always go by it, mind you, but I like to check it. 

an example:
http://www.avon-tyres.co.uk/motorcycle/roadrider

thanks for the link. they carry the sizes I was looking at and the rim rec. is right on.

[greasy j]

by the way I remember someone saying they got the wrong size spokes from Buchanan's when ordering rims. does anyone know what size I would need for this application, in case I can't trust their recommendation?

3.5 rim on 750k1 rear hub, 2.5 rim on front hub. I am using a gl1000 front end, but I am almost certain the wheel has the same hub as the 750 so I can use either.

also stainless is better than chrome, correct?

lastly, is buchanans the only place to get rims? any other good vendors?

thanks!