18 inch wheels front and rear

Who's building these Manx frames with 54.5 deg. (35.5) head angles, Uncle Bunt or Arlen Ness??

Martyn.

Fast Eddie said:

Al please give some kind of evidence for your ‘probably’.

I’ve spoken to Molnar, have you?

His frames are to factory drawings.

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What rake is Andy Molnar using ? Most Manxes in Australia have 18 inch wheels. Ken Mc Intosh in New Zealand builds Manxes with Molnar motors, but the one which Cameron Donald has ridden at Phillip Island had 19 inch wheels - he won convincingly. He is obviously an excellent rider, but there are others just as good. A frame with 60 degree rake and 19 inch wheels might be exciting. I cannot remember th name of the guy who built most of the aftermarket frames in Australia, but you could choose which rake you wanted. After the 1960s it became very rare to see a Mamx which had not been modified.
The 60 degree rake, short offset and 18 inch wheels first appeared on Japanese two strokes in the 1960s. The style of riding was completely different, but not necessarily better. If you consider 750cc Suzuki two strokes - there was a frame which I think was made by Roger Smart and used in America. Suzuki would not allow it to be used in Europe. Rod Coleman from New Zealand put Pat Hennen on it. It use to turn up at the Sandown meeting in Victoria each year, and was very competitive against the TZ750 Yamahas.
Even now, in classic racing, the older Japanese bikes do not handle very well, most of them seem to understeer a lot. I am not the most brilliant rider but the Seeley keeps up with them easily. I just have to be careful not to bounce off anyone, if I don't get a good start.

I think I am correct about that 54.5 degree rake on the Manx frame, but my knowledge of that goes back 50 years. My mate's Triton has the 1950s Manx frame and I remember asking him about that. He is the guy who wised me up about the stupidity of enlarging inlet ports when it makes the motor develop less torque. If you have a lot of torque and gear high, the torque still ends up in a similar situation, but you go quicker.

acotrel said:

What rake is Andy Molnar using ?

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To be honest, as you are the one who keep quoting specific rakes I thought you would know that ?!

I’ve never asked, so I don’t know.

All I know is that MOLNAR FRAMES ARE BUILT TO FACTORY DRAWINGS.

And that factory drawing included the rake.

So I strongly believe that Molnar frames are NOT running the radically different rakes that you keep stating.

And my evidence for this belief comes from Andy Molnar.

So I would very much like, and I strongly suggest, that you stop saying otherwise UNLESS you actually know it to be true.

Fast Eddie said:

To be honest, as you are the one who keep quoting specific rakes I thought you would know that ?!

I’ve never asked, so I don’t know.

All I know is that MOLNAR FRAMES ARE BUILT TO FACTORY DRAWINGS.

And that factory drawing included the rake.

So I strongly believe that Molnar frames are NOT running the radically different rakes that you keep stating.

And my evidence for this belief comes from Andy Molnar.

So I would very much like, and I strongly suggest, that you stop saying otherwise UNLESS you actually know it to be true.

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Sigh.

Twenty odd years ago I had the misfortune to work for Molnar for a brief period. During my time there as a CNC miler/turner I machined out the bearing bores on the head stocks of several Manx frames. Whilst I cannot remember the exact angle, so please don't quote me, I seem to think it was around the 26 degrees from vertical/64 horizontal mark. It most certainly wasn't 35.5 deg. as nobody I know races choppers.
With 2.25" yoke offset & 19" wheels this gives around 3.9" of trail.
Also, I seem to remember Ken Sprayson stating that all the Norton frames, be it Manx, Slimline, or Wideline, were the same at 26deg. If any one has his book the answer may be there.

Matt Spencer said:

Think the period Laverda's ran 18's too , so al may not be lost .

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Most italian bikes 750cc up had 18" tyres front and rear. Interestingly, BMW fitted a 19" front tyre and 18" rear on their classic R series while the K series had a 18" tyre up front and a 17" tyre at the rear, later changed to 17" at both ends. The modern R series followed suit.
Most neo-classic bikes sport a 19" front and a 18" rear tyre. Triumph however offers their street twins with 18" front and 17" rear tyres except on the Thruxton RS, which comes with 17" tyres at both ends.

- Knut

I have got myself confused about measuring rake
Those numbers stay in my memory. I am certain the Seeley has 70 degree rake, the Yamaha TZ has 10 degrees less, and an original Manx has less again. In Australia, most of the after-market Manx frames were made with the same rake as the Yamaha or Suzuki two strokes because they were intended to be used with 18 inch wheels - not 19. They handle like Suzukis - tip into corners much faster. When 19 inch wheels are used, the steering head is usually more vertical.
The steering on the 1970s Yamaha or Suzuki two stroke gives neutral steering with 18 inch wheels. The Manx with the aftermarket frame steers similarly to a Suzuki two-stroke. Both have 18 inch wheels, and so does the Seeley.
With a Commando, you have more yoke offset, so less trail. When you fit 18 inch wheels instead of 19, you reduce the trail even further.
If you remember, the first Commandos has steering geometry specified by PW. The yokes were changed to make the Commando more stable. Fitting 18 inch wheels would make it even more stable.
With my Seeley, if I counter-steered to tip into a corner, it would itself into a knot and crash.
There is also an effect on whether the bike oversteers or understeers in corners. When you counter-steer to tip into corners, that is because the bike is understeering. when the bike tends to run wide as you accelerate out of corners that is also under-steering. Both are caused by reduced trail.
My Seeley has a lot of trail, so it over-steers both going into and coming out of corners. You would not that on a road bike because you would have to stay awake.

I'm a little late to this party, but here goes. I've ridden and raced Commandos with 19" tires front and rear and with 18" tires front and rear. Never did manage to try 18" rear with 19" front, but plenty of others have. They all work. They work better if set up properly, i.e. proper rim widths and tire sizes and profiles, maybe slightly longer shocks in some cases, but unless you get pretty weird with the tire sizes, They are not the death traps Al seems to believe. I even put 17" slicks on my Commando PR one time at Daytona, at the insistence of a friend whom I let race the bike. It was a mistake, but not because of the handling. It just didn't have enough ground clearance in the corners. If we had been able to raise the height a bit, it would probably have worked well.

Rob Tuluie on my Commando PR at Daytona on 17" slicks.

Probably maybe were & by then I've switched off.

One thing of which I became aware when I first started racing is most of our Australian circuits are very tight. If the circuits are big and flowing such as Phillip Island, it does not mater so much if your bike's handing is more stable. But on a short tight circuit more trail gives more benefit. If you get into a corner too hot and your bike oversteers, you can trail the brake until you lose enough speed then get back on the gas before you reach the end of the bitumen. You do not usually ride like that on public roads.

I have been thinking about the rake angles I mentioned. When you make a frame, you usually use a frame jig. The 70 degree rake on the Seeley is the angle the bar through the steering head makes with the base of the jig. For 10 degrees less rake, you increase the angle of the bar by 10 degrees. That gives you a rake of 60 degrees. For a Manx frame of 54.5 degrees, you would increasse the angle of the bar by another 5.5 degrees. When you are doing it, it is east to make a mistake.

Jackman said:

What's your thoughts on 18 inch wheels, front and rear? Me well I think 19's front and rear look weird and probably don't help in the handling department and also when shopping for a 19" rear tire our options are kind of limited . Next year I'm probly going to have 18 inch wheels laced up.

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I have 18" wheels on my 850. It handles fine. It must lower the bike by almost 1/2" which can't be good for ground clearance, but I haven't noticed any problem. I did it by accident. My bike has RD400 Mag wheels, instead of standard Norton wheels. I built it this way because I think it looks good also a friend gave me the wheels. I didn't realize the front was an 18 until I found out the 19" tire wouldn't work. I knew he rear was an 18". A lot of people prefer the 18 on the back as it gives a much greater variety of suitable tires that can be chosen from. You may have some problem getting the front fender to look right. If I was you I would go with 19" on the front. I have looked at SR500 front wheels because they are 19" and would match the rear wheel I have in design.

acotrel said:

I have been thinking about the rake angles I mentioned. When you make a frame, you usually use a frame jig. The 70 degree rake on the Seeley is the angle the bar through the steering head makes with the base of the jig. For 10 degrees less rake, you increase the angle of the bar by 10 degrees. That gives you a rake of 60 degrees. For a Manx frame of 54.5 degrees, you would increasse the angle of the bar by another 5.5 degrees. When you are doing it, it is east to make a mistake.

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I've built frames for a living for over 20 years.

You can't mess up by 5.5 degrees without all your miters being terribly off, nothing fitting in your jig, and it coming to your immediate attention. 5.5 degrees is a HUGE amount. That's not a possible mistake on a navigable frame, that's someone making things up to save a turd they floated on a forum in the conversation a few posts ago.

This is crazy talk and the kind of thing that turns people off and degrades this forum. You're speaking out of your ass.

tricatcent said:

I have 18" wheels on my 850. It handles fine. It must lower the bike by almost 1/2" which can't be good for ground clearance, but I haven't noticed any problem. I did it by accident. My bike has RD400 Mag wheels, instead of standard Norton wheels. I built it this way because I think it looks good also a friend gave me the wheels. I didn't realize the front was an 18 until I found out the 19" tire wouldn't work. I knew he rear was an 18". A lot of people prefer the 18 on the back as it gives a much greater variety of suitable tires that can be chosen from. You may have some problem getting the front fender to look right. If I was you I would go with 19" on the front. I have looked at SR500 front wheels because they are 19" and would match the rear wheel I have in design.

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RD wheels on a Commando now that’s cool , must have been a lot of work to get them to fit.

I have have a Kawasaki 400 triple with 18 and 18 that’s a big part of why I will be going to 18’s , lower looks better imop and I hope it handles as well with 18’s .

I have 18” front and rear on my Commando.
Works great.

tricatcent said:

I have 18" wheels on my 850. It handles fine. It must lower the bike by almost 1/2" which can't be good for ground clearance, but I haven't noticed any problem. I did it by accident. My bike has RD400 Mag wheels, instead of standard Norton wheels. I built it this way because I think it looks good also a friend gave me the wheels. I didn't realize the front was an 18 until I found out the 19" tire wouldn't work. I knew he rear was an 18". A lot of people prefer the 18 on the back as it gives a much greater variety of suitable tires that can be chosen from. You may have some problem getting the front fender to look right. If I was you I would go with 19" on the front. I have looked at SR500 front wheels because they are 19" and would match the rear wheel I have in design.

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This will depend on the tyre profile. From memory, an Avon RoadRunner 4.00-18 had virtually the same diameter as the 19" tyre originally used on the Commando, so the ride height would not change, while Conti's were definitely smaller.

I have 18" wheels on my bike as well and I haven't noticed any problems with ground clearance or handling. I actually stumbled upon it accidentally because a friend gave me RD400 Mag wheels and I thought it looked good. However, it might be harder to find suitable tires for the front wheel if you stick with an 18". I would suggest going with a 19" on the front, like the SR500 front wheel, which would match the design of the rear wheel you have. I remember reading somewhere that the Avon RoadRunner 4.00-18 had almost the same diameter as the 19" tire originally used on the Commando, so the ride height wouldn't change much. But the Conti's were definitely smaller.

I have 19/18” setup. WM2 for front and WM3 for rear. I run a Shinko 712 series tire with a width of 100/90/19 and 120/90/18. I think it looks good and handles just fine. The Shinko tires are cheap and mine balanced out real well.