Suspension questions

[gerryrichards]

Hi all,

Just a couple of questions re Roadster suspension from a relative Marlin newbie:

- if a Roadster has Marina rear springs and they have 3 leaves as opposed to 2, does that mean that they are van springs - possibly, probably, definitely or inconclusive?

- the 3 roadsters which I've driven all had marina based front suspension and all drove well but lacked steering self-centring force and to my mind this gives a slight sense of 'steering vagueness' to an otherwise very good driving experience. As this is normally due to a lack of front caster, is this a design flaw of Marlin front suspension (or feature in a quest for light steering....?), do most owners live with it or has anyone tried to remedy it with e.g. top link modification or increasing front ride height slightly in relation to rear?

The forum is a great resource but so far my searches have proved fruitless in providing answers to the above - but please let me know if existing threads have already covered this...

Cheers!

Gerry

[dcunn]

Re: Suspension questions

Have you looked in Tech Tips ?

Also try the search function, typing in "Roadster caster angle" starts you off with four threads

(I didn't look at them)

[gerryrichards]

Re: Suspension questions

Thanks, will give searching another go!

[ggrum]

Re: Suspension questions

The low level of steering self centring on the Marina based Roadster is a common problem and the castor angle is, in theory, non adjustable. Some members have slightly increased the castor angle by replacing the front tie bars with adjustable ones and pulling the bottom of the strut forward slightly but I think you have to be careful here to avoid putting residual strain in the suspension components. You can also play around with the shims in the Mini top arm but the same argument applies. Personally I found that ensuring the bottom trunnions were well greased and that the steering rack was not over stiff helped to improve the self centring.

[ggrum]

Re: Suspension questions

Happy to be corrected on this but I believe the ideal caster angle for good self centring is about 6 deg whereas the Marina set up is 2 to 3 deg. This may have been ok on the Marina (never driven one personally) but is not really enough for the Roadster. You do get used to it though.

[gerryrichards]

Re: Suspension questions

Thanks for the feedback - I do remember getting used to it driving my late father's Marlin (about 20 years ago...) it's just that I'm used to steering which weights up nicely in corners. Narrower/taller tyres can help with self-centring force too, so might experiment with different tyre sizes at some point.

[FranklinLeicester]

Re: Suspension questions

I agree with the above. When I converted from 13” 185 tyres to 14” 165 there was a big improvement but generally it is something we just live with.

[gerryrichards]

Re: Suspension questions

Yep - drove my newly purchased car back from Leeds to Manchester today. It's on 185/60/13 and steering is pretty 'wanderey' - but the plan is to fit MGF 14" steel (spare) wheels and either 175/70/14 or 165/80/14 tyres. Should give dual benefits of more assured steering feel and improved ground clearance (end goal is to do some trials)

[lizbillings]

Re: Suspension questions

Worth checking tyre pressures. Maybe too high.

[HairyDave]

Re: Suspension questions

Possibly get the tracking checked, Mine was toeing OUT! Very weird steering!

[Gareth]

Re: Suspension questions

Worth checking tyre pressures. Maybe too high.

I agree. Check tyre pressures. I run mine on 18psi and it transformed the handling and made for a far less bumpy ride! Think how light the car is now compared to it's doner car! Gareth.

[gerryrichards]

Re: Suspension questions

Yes, we didn't have a tyre pressure gauge when I picked the car up so couldn't check before I drove it home, but suspect that they're a bit on the high side.

I can check the tracking as I have a really accurate home made tracking gauge which we used to use when we were hillclimbing Imps and Ginettas.

I was always messing about with suspension geometry, spring rates, tyres/tyre pressure, different dampers etc back in those days as we figured it was the best way to try and beat the bigger cars with more bhp! My Marlin has a standard 2.0 pinto engine with about 95 bhp (?) - I can't tell you how much money it used to cost us to try and get 90+ bhp out of a 998cc Imp engine...!