Understeer ?

[G JONES]

Thoughts & sensible suggestions on reasons for understeer on a 3 wheeler....
Now - I might be looking for no good reason here - at Anglesey this last weekend - we were getting bad understeer at the exit of 2 particular corners - Rocket & Peel - now if everyone else is having similar things going on - I'll forget about it - but - having put a full new set of Avons on the bike (instead of 9 year old Yoko's) - I was hoping it might be a bit tighter on the front end - Matty - who was passengering - said he was working the front as much as possible - and watching me giving it full lock - but going sideways...
The bike was faultless everywhere else - so is there anything more - or different I can do ? (other than eat more pies myself)

[ChrisWells]

I assume we are talking about right hand corners (and a left side chair)?
Move chair wheel back if adjustable?
Move motor and/or fuel forward? (before going to that trouble bolt some weights on forward to confirm it helps)
I would have my passenger climb up on my back a bit for the odd corner where understeer was an issue, lost a bit of drive but the minor oversteer helped get the bike pointed in the right direction.
On the F1 we were advised to carry more speed into and trough the corner, a bit scary with trackside armco but it seemed to help a bit. Problem was less pronounced on the F2 but it seemed to respond in a similar manner.
Good Luck
Chris

[tonybsa2008]

Obviously as we discussed yesterday Gordon,on one of the corners you mention the road drops away as you go round the corner.4 strokes will probably have less trouble than we do becuase they dont need to carry as much apex speed as we do.

[G JONES]

Obviously as we discussed yesterday Gordon,on one of the corners you mention the road drops away as you go round the corner.4 strokes will probably have less trouble than we do becuase they dont need to carry as much apex speed as we do.

Yes Tony - have to explore any possibility of improving the situation though...
It could well be it's just the nature of the circuit on those corners - but if there's any way of improving the situation - I'd like to find it
I guess most folk would say my 8.5st isn't helping

[criso]

I was really struggling with the right hander before the corkscrew, having to let the bike turn underneath me with next to no throttle on and catch it with the throttle to get it to turn. We moved our sidecar wheel back too which helped. You could also maybe look at putting less pressure in sidecar tyre to get it to pick the back end up a little??

[G JONES]

I was really struggling with the right hander before the corkscrew, having to let the bike turn underneath me with next to no throttle on and catch it with the throttle to get it to turn. We moved our sidecar wheel back too which helped. You could also maybe look at putting less pressure in sidecar tyre to get it to pick the back end up a little??

Thanks Sam - that's really helpful to know it wasn't just me - or the bike - but more to do with that corner...
I can't move the chair wheel back / forward - I can adjust toe / lean in reasonably easily though - but hadn't thought about doing it - thinking about it a bit more - our old shelbourne had a lot of toe in - and I seem to remember it being better around that corner...
I did have a suggestion to lift the back end too - not a lot of adjustment there - but maybe enough to improve it...

[criso]

Yeah try giving it more toe that will help. What pressure were you running in the sidecar tyre? Could maybe drop a few pounds to get it to grip more and might help the back slide round

[ianw]

Hi Gordon, if I remember correctly??? the overall diameter of the Avon tyre is greater than the Yoko, could possibly affect the handling???

[G JONES]

Yeah try giving it more toe that will help. What pressure were you running in the sidecar tyre? Could maybe drop a few pounds to get it to grip more and might help the back slide round

Yes - I'm kicking myself now for not trying a bit more toe in - would have been a 5 minute job - but never thought at the time - was the first time I've ever had 3 new tyres on a bike too - chair tyres have always been cast offs - but I'd wanted to try the new bike with full set of good tyres since I built it...
We were running what Steve Smith suggested F R S 13 / 12 / 16

[G JONES]

Hi Gordon, if I remember correctly??? the overall diameter of the Avon tyre is greater than the Yoko, could possibly affect the handling???

Hi Ian - tyre diameters I've spent ages looking at - mainly to try find a cheaper usable alternative - not found anything yet !
Avon sizes we use:
6.2/20.0-13 diameter = 505
7.2/20.0-13 diameter = 513

Yoko Y801:
160/515-13
180/515-13
(Might be 185 actually - have to check)

I'd love to try try the Yoko semi slick - but they all appear to be a bit too tall - and I really don't have a clue how much taller would be ok without affecting how the bike handles (would save a lot of money mind ! )