oversprung rear?

[AndyAshworth]

the std TRX spring rate is suited for a 76kg rider but the weight of a TRX is around the 207kg mark std..

No wonder I've always enjoyed the TRX ride. I weigh 76kg. How lucky.

I wish I was lucky enough to weigh 76kg

[Stankflapper]

I get no sag from grabbing the throttle

You shouldn't get any sag from grabbing the throttle and hard acceleration. The back end should actually lift up if anything.

its true

the only thing that lifts from hard accel on my bikes is the front wheel.. I think you are confused

[fung]

'the only thing' 'thats hard' 'lifts on acceleration'
Cheers
Fung

[coxylaad]

Any of you ever read a book called A Twist of the Wrist by Keith Code.

I recommend you read it, there is also a dvd available to download too. its awesome, explains everything what is happening with both the bike and you through the whole range of motorcycling situations - including the one above.

[coxylaad]

try this one:

http://www.msgroup.org/Tip.aspx?Num=080

couldn't be arsed to read it but the pictures look like they are saying the right stuff

[dandywarhol]

I go with whats in the link but there's still more to it and that's to do with the position of the swing arm pivot/gearbox output centre line and general weight transfer under acceleration

[coxylaad]

yes there are a few factors that influence this but as an example watch this:

http://www.youtube.com/watch?feature=pl ... 9MRsFZJ2Hk#!

note when the bike is gassed the back end lifts up, demonstrating the principle

[dandywarhol]

I'm not argueing with you Ian - I've watched my own bike lift on the dyno but in reality other factors more than cancel it out and make the back end squat down to improve grip - except the ol' Beemers which rode up the final drive pinion

[Stankflapper]

As a result, the motorcycle moves forward and, because the upward force is behind the bike's CG, the rear-end of the bike moves UP. You will also observe if you look closely that as the angle of the swing arm increases, the wheelbase decreases. THAT is the significance of an upward pointing swing arm.

I suppose it is the way you interpret. To me it simply means you are doing a wheelie

[Stankflapper]

I'm not argueing with you Ian - I've watched my own bike lift on the dyno but in reality other factors more than cancel it out and make the back end squat down to improve grip - except the ol' Beemers which rode up the final drive pinion

The dyno lift effect is the rear wheel trying to climb the roller, this is why they are tied down.