Manx vs Petty Manx, what are the differences?

He made a few road-going frames for twins as well, but details are scant. Sure would like to see some numbers on both of them, the Tickle T5, and the Lowboy. They sure look small.

Matt Spencer said:

G M A Engineering .

looks like its oil in flame .

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The tube down from the headstock to the cross piece is a good idea. Friends using McIntosh Manx frames for Velocettes take two tubes down from the headstock to the top rail. One either side..

Wheel size affects the trail. If Petty frames are designed for 18 inch wheels, they will have more rake on the steering head. In about 1970, it became much more difficult to get good runbber in 19 inch tyres. You have the same problem now, Where can we get good 18 inch tyres ?
In the 1970s in Australia, the aftermarket frames had increased rake for 18 inch tyres, the bikes handled like Suzuki two-strokes. An original Manx usually oversteers more as you accelerate. That is why they improve your riding technique. The others stay more neutral.
After the last time I rode my Seeley, I wound the rear shocks up a notch, to slow it's rate of turn when I accelerate when on a lean. I felt it had a bit too much oversteer.
The frame geometry is critical and it can be dangerous.
When you look at that Petty frame, it is not just a frame. You do not know what it will do until you set it up and ride it. When I first ride any motorcycle, I am always very careful until I know what it does when accelerating and braking. If it is wrong, a problem can come from nowhere and grab yoiu by the throat.
A lot can depend on where the bike's centre of gravity is positioned.

If the bike oversteers more when you accelerate, you can gas it much harder when on a lean in corners. But if the motor is too far back in the frame, the bike might destroy your confidence. Some people believe a 50-50 weight distribution is good - they are idiots. That light and airy feeling is not nice whrn you are going like buggery in a corner.

Some info here.



Road frame info from a site member that hasn’t posted in a while.

kernel65 said:

Some info here.

Petty Manx Norton 350cc Replica - The Classic Motor Hub

The motorcycle we are proud to offer for sale is a Replica of the Petty Manx 350cc. This Petty frame kit was acquired by Ray Petty’s family 15 years ago and it was built up to a complete bike around 5 years ago for Ray’s Grandson

classicmotorhub.com

Road frame info from a site member that hasn’t posted in a while.

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I believe that's from Jeff. He sold his frame and motor off and never completed his project. Wonder where it went...

Looking at the details on that write-up, it's no wonder the tubing cracked, if it was a high carbon 1.125" at .056" wall, that's pretty light! Made for speed, not the long haul.

Storm 42 bought a Petty chassis and will be racing it this year. He says it really is quite small. Also that the engine is in a different position to a stock Manx, being further forward in the frame to get more weight more forward. So there are perhaps more changes than are first apparent.

Fast Eddie said:

Storm 42 bought a Petty chassis and will be racing it this year. He says it really is quite small. Also that the engine is in a different position to a stock Manx, being further forward in the frame to get more weight more forward. So there are perhaps more changes than are first apparent.

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If the rake on the steering head is 26 degrees and the wheels are 18s, when the motor is forward, the handling is likely to feel heavy. If the rake is 24.5 degress and the wheels are 19s, when the motor is forwarnd the handling feels light, and better. But these days, where cqan we buy 19 inch tyres , or even 18 inch ?
A 1950s BSA Gold Flash frame has 26 degree rake. With 1960's fork yokes and 18 inch wheels, they are pretty good and reasonably priced when you find one. But might not be tall enoungh for a Commando motoor. They are a frame which very few people use - with the original BSA yokes, they mishandle.

Ken (Fullauto) has seen my Seeley 850. He remarked on how small it is. If a Petty frame was cheap, I would buy it. But a Seeley frame is the nect generation. In the mid 1960s, the best British single cylinder motor cycle was the Seeley 7R Matchless. Many people are obviously committed to racing in a certain class, and that probably reduces their options. When I built my bike, it was built to be what was racing back then. The Gus Kuhn Seeley Commandos gave the Norton factory bikes a run for their money. I did not care where it might fit in historic racing. In Australia, historic racing is bullshit. Most of the participants do not know how to race, because they never have.
There is a belief that bigger is always better. It disregards the truth. In the 1960s in Australia, there was an Allpowers A grade class which used to separate the men from the boys. Most races in that class were won by Manx Nortons - not Norvins ot 650 Triumphs. Then the two-strokes came along and blew them all to the weeds.

t ingermanson said:

I believe that's from Jeff. He sold his frame and motor off and never completed his project. Wonder where it went...

Looking at the details on that write-up, it's no wonder the tubing cracked, if it was a high carbon 1.125" at .056" wall, that's pretty light! Made for speed, not the long haul.

Click to expand...

Yes, it was from Jeff. Can’t remember who/where the project went. He had a lot of rare/trick parts to go with it.