Any suspension design changes required?

[Transmitter Man]

I'm looking to increase wheel size from 15" to 17" while going to a corresponding lower profile tyre to keep rolling radius the same or similar.

At the same time I'll be refreshing, or if need be replacing my coil over shocks all round (TVR wedge).

What if any changes should I make to the suspension or spring rate to compensate these changes?

Thanks.

Phil
TVR 420 SEAC

[Sam_68]

No, I wouldn't worry about it.

You'll be changing the spring rate of the tyre itself and may be marginally changing the unsprung weight, but not by enough to make it worth specifying different road springs or dampers to compensate.

If you're seriously concerned about damping, though, get a set of decent quality dampers with adjustable spring seats from a company with the capability to dyno test them for you, to ensure that they a matched in pairs. Similarly, get the spring rates tested to ensure that they are correct (there can be quite large manufacturing variations), and get the car corner weighted and the geometry set when you have fitted them.

[Transmitter Man]

Hi Sam,

Many thanks for your thoughts.

I have Gaz adjustable coil-overs all round at present and will be sending them to the factory for refurbishing as the previous owner used the car as his weekend tack day machine so they've had a fairly hard life.

I was considering investing in Nitrons but they do not seem to be available for my car.

Thanks again.

Phil
TVR 420 SEAC

[Sam_68]

Transmitter Man said:

I have Gaz adjustable coil-overs all round at present and will be sending them to the factory for refurbishing...

In that case, ask if they can provide you with dyno sheets for the dampers when they refurbish them.

Transmitter Man said:

I was considering investing in Nitrons but they do not seem to be available for my car.

Have you asked? Even if they don't have an off-the shelf solution, they may well be able to supply a set if you can give them the necessary information (dimensions, spring rates, sprung and unsprung weights, etc.). Coilover dampers tend to follow pretty standard dimensions (to suite standard spring sizes), so it's usually just a matter of picking a damper of the right length and stroke and valving it to suit.