Race chassis

[lodgernz]

your right , who would want to own a honda , ps whats your bucket (-;

Ummm.. getting off topic here. *cough*

So, What wheelbase do you usually aim for with the GPR frames?

[mr bucketracer]

Ummm.. getting off topic here. *cough*

So, What wheelbase do you usually aim for with the GPR frames?

i think the hole kbiker of the topic (-; , i go for 1260 ish , over the rs125 at just over 1200 , for me the bike feels more planted on the track and seem to get away with murder

[lodgernz]

i think the hole kbiker of the topic (-; , i go for 1260 ish , over the rs125 at just over 1200 , for me the bike feels more planted on the track and seem to get away with murder

Thanks for that. Yeah, my little babies feel pretty comfortable at 1220-1240. Wouldn't want any shorter though.

[timg]

your right , who would want to own a honda , ps whats your bucket (-;

Yeah, ya poor bugger I’ll take that CBR150 off your hands so you’ll feel better for Xmas

[Grumph]

i think the hole kbiker of the topic (-; , i go for 1260 ish , over the rs125 at just over 1200 , for me the bike feels more planted on the track and seem to get away with murder

I still think in inches for wheelbase - and by my standards 50in is short - that's 1270mm

But I'm not building for kart tracks...

[husaberg]

I still think in inches for wheelbase - and by my standards 50in is short - that's 1270mm

But I'm not building for kart tracks...

That MB100 you tuned was about 48 was it not?
Bet the rider still would have liked it to turn sharper around the hairpin at Greymouth.

[Grumph]

That MB100 you tuned was about 48 was it not?
Bet the rider still would have liked it to turn sharper around the hairpin at Greymouth.

A/ I was forced to use that chassis - at least I made it around 3 times stiffer than stock...But still not directionally stable at that power level - with me on board anyway. Frightening actually.

B/ That rider was/is under the impression that gutters and kerbs are part of a race circuit and are there to be used...If he was in the gutter at the hairpin, it was intentional...

[mr bucketracer]

That MB100 you tuned was about 48 was it not?
Bet the rider still would have liked it to turn sharper around the hairpin at Greymouth.

i cant wait to drop the lap record by 5 seconds

[Grumph]

i cant wait to drop the lap record by 5 seconds

Husa will know - but I think it's Al Hoogie ? Let me know and I'll be there to watch you try.

[mr bucketracer]

Husa will know - but I think it's Al Hoogie ? Let me know and I'll be there to watch you try.

apart from the last one 5 second would of been easy , make the stakes high i think lol , apart from i'v lost it

[husaberg]

Husa will know - but I think it's Al Hoogie ? Let me know and I'll be there to watch you try.

probably still is hoggie
but if revingtons hotel demolition goes ahead it might give the chance to run greymouth in reverse direction, As its removal would give a run of for the back straight.
Assuming they removed the kerbs. It might be great fun to wear out the left side of a few tyres.
It would be a dam sight faster as well. likely be even safer too.

[Frits Overmars]

then you remember you don't want to be like everybody else!

I don't want to be different. But the missus keeps telling me that I am .

I still think in inches for wheelbase - and by my standards 50in is short - that's 1270mm. But I'm not building for kart tracks...

Neither were Aprilia, Derbi, Honda and KTM (in alphabetical order).
But they all established that 1270 mm was too long for 125cc GP-racers on GP-tracks, and ended up with about 1215 mm (47,8" in Grumph currency).

That MB100 you tuned was about 48 was it not? Bet the rider still would have liked it to turn sharper around the hairpin at Greymouth.

There you go Grumph.

I was forced to use that chassis- at least I made it around 3 times stiffer than stock. But still not directionally stable at that power level- with me on board anyway. Frightening actually.

Racebikes are not meant to be directionally stable. H-D are catering for stable.
The majority of 500cc GP-bikes were shaking like mad on the straight-aways, but when I asked their riders about it, they didn't even know what I was on about;
none of them registered unstable bike behaviour as anything peculiar. They were more concerned about their bike being too lazy turning in.

That rider was/is under the impression that gutters and kerbs are part of a race circuit and are there to be used...If he was in the gutter at the hairpin, it was intentional...

That rider was right. I remember drifting against a kerb in a corner. The first time was unintentional, but then I realized I could give it full throttle while against that kerb.
You gotta use what you come across.

[Grumph]

I'd love to get you on that MB100, Frits, making a rubber band three times stiffer doesn't change it from a rubber band, LOL.

Yes, I do appreciate what benefits a short wheelbase offers. I do build as short as possible given the engines and suspension constraints I'm frequently forced to work under. I also understand the geometrical quandries that riders find themselves in when trying to get a bike to turn. Jack up the back - drop the front - then hang on for grim death.

As an interested observer, I've watched tyre development and talked to riders here. It would appear that some brands have adopted a carcase construction which is more directionally stable than others. Some turn very readily - which seems to mean that those brands suit a stable chassis better.

On coming back and re-reading Frits post above, I'd add that i'm not building for GP circuits either. Anything I build is very likely to be used on the street circuits here in NZ - which are littered with bumps. surface changes and manhole covers. Both from observation and talking to riders, a GP focused chassis such as Honda RS125's or TZ's are not a comfortable ride on those tracks.

[Frits Overmars]

Anything I build is very likely to be used on the street circuits here in NZ - which are littered with bumps. surface changes and manhole covers.
Both from observation and talking to riders, GP focused chassis are not a comfortable ride on those tracks.

You should have a chat with Rossi .

[Grumph]

This is one of my engine customers. While I'd love to talk to Rossi, I think I got the gist of what it feels like from this.