Author Topic: What's the highest rated tire you can put on a stock cb750 rim?  (Read 12494 times)

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Offline Pak Ramstock

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What's the highest rated tire you can put on a stock cb750 rim?
« on: January 23, 2011, 12:05:37 AM »
What's the highest rated tire that will fit on stock rims for a Honda cb750f? I'm currently running H-rated Metzeler's (up to 130 mph) but haven't seen any V or Z-rated tires that will fit on the stock rims. Am I just not finding them, or are they just not out there? I made some off-season mods that I'm pretty sure will push my old Honda over the 130 mark, and am trying to figure out if all I need to buy are tires or if I'll need to look into different rims, swingarm, etc

Thanks.

Offline sabat

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Re: What's the highest rated tire you can put on a stock cb750 rim?
« Reply #1 on: January 23, 2011, 12:29:35 AM »
We could give you better advice if we knew the diameter and width of the wheels.  :-D

Offline Pak Ramstock

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Re: What's the highest rated tire you can put on a stock cb750 rim?
« Reply #2 on: January 23, 2011, 02:04:04 AM »
Hmmm, you might be on to something there! Here you go:

Front tire: 110/90-19
Rear tire: 120/90-18

Both rims are laced and the tires are tubed.

Offline sabat

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Re: What's the highest rated tire you can put on a stock cb750 rim?
« Reply #3 on: January 23, 2011, 08:53:52 AM »
For those sizes, probably the pushrod folks would have more info. If it were me, I'd install one piece wheels over 125mph.

These tires are for tubeless applications, but the Bridgestone Battlax BT45 is V-rated in those sizes. I've heard of folks running tubes in tubeless tires. Check with the tech director of your sanction. Also the Conti TKV11 comes in a 19 and is V rated.

But 130 is fast for a CB750 - how fast have you really been?  Got some pics?  :-D

Offline Cajun Kid

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Re: What's the highest rated tire you can put on a stock cb750 rim?
« Reply #4 on: January 23, 2011, 10:36:02 AM »
130 MPH is very fast for a N/A CB750... I would love to see that bike,, I had several CB550 and CB750 's back in the day and never got to 120 mph (around 115/118 was tops for me).

Are you going to run the CB750 at Maxton ?

Charles
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Offline Pak Ramstock

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Re: What's the highest rated tire you can put on a stock cb750 rim?
« Reply #5 on: January 23, 2011, 11:15:18 AM »
Raced with the 750 at Maxton twice, in 2007 and 2009, and at Bonneville in 2007. Of the three events, my best was the '09 Maxton meet, where I ran 114.3. I'd had the motor's upper end rebuilt with a mild road-racing cam, plus I'd changed the front and rear sprockets to give me taller gearing, but otherwise the drive train was bone stock.

Since then, I've had the motor completely rebuilt and bored out to a 970. In addition I threw on CR carbs, replaced the Dyna ignition with a PowerArc optical one, had the gears undercut, etc. I'm taking it to a shop to dyno test it next weekend, and that *should* finally get it dialed in all the way. A new cafe seat and rear sets are on their way soon, too, so I can lay down closer to the tank.

I can't say for sure it'll top 130, but given my experience riding it not tuned all the way, my hunch is it will. That's why I'm so concerned about the frame, tires, etc, being able to handle it. Anyway, hope that helps. Oh, and attached are two pics - one from Bonneville when it was still a 750, and one from the shop late last year after we'd rebuilt it as a 970. And yes, I do plan on racing at Maxton with it in 2011, just not sure which meet, though!

Thanks for all the help, by the way!

Offline Pak Ramstock

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Re: What's the highest rated tire you can put on a stock cb750 rim?
« Reply #6 on: January 23, 2011, 11:24:38 AM »
Also, got any ideas as to what kind of one-piece wheels might be an exact replacement for the stock laced ones? I know Honda's old Comstar rims might work but wondered if there was anything else out there that would just bolt right in, so to speak.

Offline sabat

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Re: What's the highest rated tire you can put on a stock cb750 rim?
« Reply #7 on: January 23, 2011, 02:55:58 PM »
Not sure on the wheels.

Regarding speed, I don't want to be a Debbie Downer, but this is how the math works out. If the fastest you've been is 115, with let's say 75hp at the wheel, to be generous, then to go 130, you'd need another 33hp. If your new controls cut your drag a fair bit, let's say 28hp. Do you think the motor work will get you that much power? 

Thanks due to Sumner Patterson for his helpful Excel spreadsheets;

http://purplesagetradingpost.com/sumner/bvillecar/bonneville-Index.html

Dean

Offline Pak Ramstock

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Re: What's the highest rated tire you can put on a stock cb750 rim?
« Reply #8 on: January 23, 2011, 04:49:50 PM »
At this point I'm not sure how much more horsepower the 970 makes, so it may well not hit 130. I should have a lot better idea about torque, horsepower, and top end, though, after I get it on the dyno. That being said, I want to plan ahead in case it does break 130. I'd hate to have the head room on speed but have to hold back because of tires.

Offline JimL

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Re: What's the highest rated tire you can put on a stock cb750 rim?
« Reply #9 on: January 26, 2011, 02:19:11 AM »
Actually.....the pic below was taken at Speed Week '69.  This 750 ran around 130 (I believe a little over) before handling problems (?) resulted in some damage (rider shown getting ready for a run).  

At the same event, my stock valve, stock port, stock carb CB450 ran a best mile of 124.65 and a C motor record of 121.102.  It also ran 118.733 un-faired.  All with just high-comp pistons, Precision Machining cams, velocity stacks and open megs.  Just coincidence we both had gold fairings.

Yes...you can go 130+.

Best of luck and they sound wonderful for us spectators!

JimL
« Last Edit: January 26, 2011, 02:27:12 AM by JimL »

Offline wobblywalrus

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Re: What's the highest rated tire you can put on a stock cb750 rim?
« Reply #10 on: January 27, 2011, 12:00:37 AM »
Careful tuning, good setup, and some basic aero work will get you over 130 on your Honda.  Last year we were just under 130 on a production frame Triumph with 70 rear wheel horsepower.  Your Honda with the new motor will probably make a lot more power than the Triumph.

Offline Pak Ramstock

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Re: What's the highest rated tire you can put on a stock cb750 rim?
« Reply #11 on: January 27, 2011, 11:09:54 PM »
Thanks for the advice and support guys. This weekend I'm taking in the CB for some dyno runs. I'll keep you posted as to what we find out.

Offline Dakzila

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Re: What's the highest rated tire you can put on a stock cb750 rim?
« Reply #12 on: January 28, 2011, 11:42:00 AM »
What's the highest rated tire that will fit on stock rims for a Honda cb750f? I'm currently running H-rated Metzeler's (up to 130 mph) but haven't seen any V or Z-rated tires that will fit on the stock rims. Am I just not finding them, or are they just not out there? I made some off-season mods that I'm pretty sure will push my old Honda over the 130 mark, and am trying to figure out if all I need to buy are tires or if I'll need to look into different rims, swingarm, etc

Thanks.

If you want to have V rated tires shaved they're good to 200 mph.

I have an A/G 1000cc bike and run V rated Bridgestones tires that have been shaved.  100 X 90 X19 V on the front and 140 X 80 X18 V on the rear with a 3 inch rim.

As for speed vs horsepower..I make 91 HP at the rear wheel, the bike and I weigh 607 lbs, ready to run. My top speed at El Mirage is 138mph and change.

Good luck with your project,

Buzz1513B
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Offline dadsolds

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Re: What's the highest rated tire you can put on a stock cb750 rim?
« Reply #13 on: February 02, 2011, 12:05:47 PM »
Hi,
I ran 120 last year at the BUB with 60 hp on the chassis dyno out of my '79 cb750L(DOHC). Everything was stock except a 4::1 Mac exhaust, some K&N pods, a Dyno 2000 ign, and a jet kit. This year I plan to run a little faster, 130, and I figure it'll take about 75 hp at the rear wheel.
I'm going to run the stock 19" comstar in front and a 18" comstar off an F model in the rear. Avon makes a V rated tire series for the stock rim sizes.
I think they call it their Road Rider A26 series. I'm not sure how these work in a spoked wheel with tubes.
Hope this helps,
Bruce
Brain says no, right hand says go
1979 UJM 750

Offline saltwheels262

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Re: What's the highest rated tire you can put on a stock cb750 rim?
« Reply #14 on: February 02, 2011, 01:04:56 PM »

 I'm not sure how these work in a spoked wheel with tubes.
Hope this helps,
Bruce


check and make sure you can run a tube
w/ a tubeless tire.

franey
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