Author Topic: Dyno run - Old worn flat rear tire better than new?  (Read 1897 times)

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Offline PeWe

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Dyno run - Old worn flat rear tire better than new?
« on: June 02, 2017, 03:24:30 AM »
I have a scheduled Dyno run 2 weeks ahead from today (no chance to get an earlier time). I have plans to replace rear tire that is worn flat and cause bad handling.
- Should I wait to replace the tire until after dyno run due to the grip? Flat tire will have better grip, right?
- Or it does not matter?

I expect around 95rwhp and plenty of torque.
Goal is 100rwhp but the 4-4 exhaust limit @ 180-200kmh.
CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline MRieck

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Re: Dyno run - Old worn flat rear tire better than new?
« Reply #1 on: June 02, 2017, 03:39:31 AM »
Use the worn out tire on the dyno
Owner of the "Million Dollar CB"

Offline mec

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Re: Dyno run - Old worn flat rear tire better than new?
« Reply #2 on: June 02, 2017, 10:16:42 AM »
A good dyno shows you the numbers with "slip" or without. Depends on how the software is set.
Mec
Honda Monkey
Takeuchi TB 070
Massey Ferguson

Offline Sam Green Racing

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Re: Dyno run - Old worn flat rear tire better than new?
« Reply #3 on: June 02, 2017, 03:04:20 PM »
PeWe, It's correct what Mike and Mec say.
When testing for RWBH, always use a worn tyre as a dyno can make a mess of a perfectly good tyre.
When using a dyno to figure out the speed of a bike, always use a good tyre as the circumference and radius can be greatly reduced due to the wear and can alter the gearing like you wouldn't believe but you still run the risk of spoiling a good tyre.
C95 sprint bike.
CB95 hybrid race bike
CB95 race bike
CB92
RS 175. sprint/land speed bike
JMR Racing CB750A street ET drag bike

Offline PeWe

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Re: Dyno run - Old worn flat rear tire better than new?
« Reply #4 on: June 03, 2017, 10:21:03 AM »
Thanks guys!
I had a feeling that the worn flat tire is better for dyno. I have started to worry about the rear wheel and how much torque the spokes can take. Honda std wheel.
CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline Sam Green Racing

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Re: Dyno run - Old worn flat rear tire better than new?
« Reply #5 on: June 03, 2017, 05:09:27 PM »
PeWe, mine has been dyno tested a few times with a stock 1976 wheel with close on 100 bhp going through it.
You should be ok if your spokes are in a reasonable condition.
C95 sprint bike.
CB95 hybrid race bike
CB95 race bike
CB92
RS 175. sprint/land speed bike
JMR Racing CB750A street ET drag bike

Offline PeWe

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Re: Dyno run - Old worn flat rear tire better than new?
« Reply #6 on: June 03, 2017, 11:09:31 PM »
Ok, my wheel should make it too then. I've noticed that some spokes need to be tightened. I think the extra torque the 1005cc provide has stressed the wheel.
CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline seanbarney41

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Re: Dyno run - Old worn flat rear tire better than new?
« Reply #7 on: June 03, 2017, 11:45:41 PM »
Ok, my wheel should make it too then. I've noticed that some spokes need to be tightened. I think the extra torque the 1005cc provide has stressed the wheel.
time to stop messing with the engine and work on the chassis.  Stock steel spoke wheels suck bad...heavy, weak, and not round.  Just upgrading to a cast wheel that is actually round and is strong enough to stay that way yields amazing dividends in riding pleasure.
If it works good, it looks good...

Offline PeWe

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Re: Dyno run - Old worn flat rear tire better than new?
« Reply #8 on: June 04, 2017, 12:39:12 AM »
I can do a wheel change if needed. My K6 will loose the OEM look if I'll use the wheels I have for my K2 build that today is parts all over the garage.
The Suzuki front wheel might fit the CB750 fork and dual brake setup. My K2 build has a complete Suzuki GS1000-78 fork with dual brakes.

It is funny...aiming to get plenty of power that ends up in other reinforcements. Dual front brakes mod has been very useful this year when the corners are thrown right into my face as never before  ??? :o My throttle hand is still used with the old setup.

I'll start to tighten the spokes. Both rims and spokes were new to season 2014. Have only done 8500km. The bike is a street bike, no burnouts or high wheelies except for the bonus low lift wheelies that happen time to time, mostly on 2:nd or 3:rd gear.
CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967