Suspension under the knife

[catretriever]

While my Griff has been in the garage getting many several bits replaced , the mechanic has been talking to me about the possibility of modifying the front suspension in such a way that the dampers may be mounted at less of an angle (i.e slightly more vertical) with the aim of increasing the amount of movement possible before hitting the stops. This involves a redesign of the front wishbones along with building out the chassis mounting point (or something ).

Anyhew, in the interests of passing the time until I get my P+J back ( it's been over a month now... ), I was wondering if any of you mechanically minded chaps would care to pass comment on such a modification.....


Matt.

[nztrev]

Are you still on the standard dampers,if so would'nt you be best investing in uprating these to the best you can buy?

Just a thought

[catretriever]

I am still on standards, and I take your point, but I think that this mod has some merit in it's own right.....doesn't it?

[GarryM]

catretriever said:

While my Griff has been in the garage getting many several bits replaced , the mechanic has been talking to me about the possibility of modifying the front suspension in such a way that the dampers may be mounted at less of an angle (i.e slightly more vertical) with the aim of increasing the amount of movement possible before hitting the stops. This involves a redesign of the front wishbones along with building out the chassis mounting point (or something ). Anyhew, in the interests of passing the time until I get my P+J back ( it's been over a month now... ), I was wondering if any of you mechanically minded chaps would care to pass comment on such a modification..... Matt.

I suppose the question must be "what are you trying to solve?" I doubt you really need more suspension travel - the standard settings are fairly soft and don't seem to bottom out (much). When upgrading most people stiffen it all up and reduce the travel.

A redesign will affect the camber and toe as the suspension moves and even the track so you'd need to be sure the changes were going to improve things. Tempting to leave well alone and just make the most of what you have with upgraded dampers etc. if you feel the suspension needs improving. Just my 2p!

[dnb]

Positive castor is a good thing. (For similar reasons to negative camber, without going into details) You may lose this if you go ahead with the plans. However, this must be balanced against the usefulness of more damper travel for use on rough roads. I can see the advantages here.

I've spent money making the Impreza struts sit MORE at an angle...

[catretriever]

GarryM said:

I suppose the question must be "what are you trying to solve?" I doubt you really need more suspension travel - the standard settings are fairly soft and don't seem to bottom out (much)

Thanks Garry. While the car was up on the ramps my mechanic was demonstrating that due to the angle at which the dampers are set, the car does indeed spend alot of time bottomed out. This mod is something he's been wanting to try and he asked me if I fancied giving it a go. He's a good, trustworthy chap with a background in racing tuscans and offered to do it FOC so I thought "What the hell"

Good point about the camber and toe, I'll have to raise this with him. I can't wait to get back in the driving seat and test it all out for myself.......I think I'd better add a £100 to the budget for a trip to Brunters

[GreenV8S]

Strut geometry issues are irrelevant to the twin wishbone setup on the Griffith though.

[shpub]

Check with your insurers first. They may not like it.

Second thing is that any change needs to be thought through very very carefully. I moved the top mounts of the shocks on the 520 and ended up having to get new shocks because the travel distances changed and I was hitting the bump stop. It also increased the twisting that was going on in the suspension. Had to increase the springing to help control that which then caused additional strain on the suspension which caused wishbones to crack. Now spent 3 months modelling the suspension and have made a new design to address these issues.

To be honest unless you know what you want to address and are prepared to put a lot of work in, I would leave well alone.

[joospeed]

Note to your mechanic .. making the dampers more vertical REDUCES wheel travel for any given damper stroke length .. you might want to get him to check his maths before attacking your pride and joy.

If however he's wanting an increase in wheel rate and willing to sacrifice some droop travel (he'll mount the top damper mounting higher and further outboard to set the same static ride height but gain in mechanical advantage at the wishbone so increasing wheel rate but reducing total wheel travel) then go ahead.

Sounds to me though that a simple increase in spring rate would get the job done with a lot less hassle.

[catretriever]

joospeed said:

If however he's wanting an increase in wheel rate and willing to sacrifice some droop travel (he'll mount the top damper mounting higher and further outboard to set the same static ride height but gain in mechanical advantage at the wishbone so increasing wheel rate but reducing total wheel travel) then go ahead.

Yes....that's the idea I think. Well done for describing it soooooo much better than me