Go Faster Advise needed please

[paul2s]

Hi Guys,

My son and I bought an IRS Striker last year, did about 8 track days six at Blyton then 2 at Cadwell.... we love doing them we did our 1st t/d this year at Cadwell 5th April,Wills best time this time was 1.48
Now we are looking for advice on how to improve what we have, in particular in the wheel dept. We currently have a set of Speedline 15" with Toyo 888 which weigh a pretty heafty 17.3 Kg each my mates team dynamics with AO48s weigh just 14Kg
Is it worthwhile to change to 13" wheels? are they compatible with the 4.4 diff ?I have been told that it is possible to do it without changing the sierra hubs If we can do it If we do what sort of top speed reduction will we get
So you have a better idea of where we are atm Current spec is as follows

2005 Raw striker
Toyota 4age 20v 1558 throttle bodies Omex 3 ecu
Quickrack
Spax suspension
Speedline 15" wheels ( 61/2") Toyo 888 tyres
Type 9 5 speed raceline st cut box 2.8 sporting close
Brakes Hi Spec fronts
Sierra rear
intrim? fixed seats ( £80 s/hand )
Roll over bar
IRS rear suspension
Sierra 7" 4.4 Raceline LSD
Car set up at Raw for track
Wt 560Kg with pretty full tank

Looking to make it lap faster, whats the best bang for the buck we can achieve?, supercharging would be great but way out of our spend. Engine pulls really well standard 20 v as far as I am aware
I was abit surprised at how heavy it was, so just thought wt reduction was the way to go. Any advice would be great
Also it would be great if we could get a few strikers / furys etc together for a trackday this year any chance of that happening?

Cheers Paul & Will

[peter030371]

Plenty of wheel speed calculators available, one on the Quaife site (http://quaife.co.uk/quaife-free-speed-calculator) another one here (http://locost7.info/gearcalc.php). Put in your current setup and then change to 13" wheels and see if you can accept the difference

Most 13" wheels should fit the front with hi-spec calipers.

On the rear you might need to 'tweak' a couple of bits on the upright ('tweak' in this sense means file a bit off and/or drop the top mounting hole down 5mm!) and on the sierra calipers the handbrake spring might be a problem but the solution to that is £18 from the Locost forum. Then some of the lighter wheels might fit.

Weight wise 4 off 13" caterham superlight wheels (as an example, I believe the Team Dynamics 1.2 are much the same) with 888 tyres will come in at about 42Kg.....giving you a saving of 27Kg on your current setup

How much do your seats weigh? That would be the next area I would look at after the wheels are sorted.

[David]

Paul & Will

Wheels: 13" are definitely the better option (significant reduction in unsprung weight, noticeably better turn-in).
When I took my 2004 IRS Striker from 15" to 13", the fronts were no problem -- however, the outboard ends of the lower rear wishbones required modification. I now use TD Pro-Race 1.2 rims with Avon ZZRs for sprinting -- excellent combination.

However, most gurus (in this case I stole it from John Tomlinson of WSCC) would say that the priorities in terms of getting faster in a cost effective manner are:
1. Seat time/instruction/advice
2. Set up
3. Tyres
4. Gearing
5. Weight
6. Power

Really annoying when you are beaten by someone whom you know to have 45 bhp less than you simply because they know how to drive

HTH

David

[peter030371]

When I took my 2004 IRS Striker from 15" to 13", the fronts were no problem -- however, the outboard ends of the lower rear wishbones required modification. I now use TD Pro-Race 1.2 rims with

I've got 14" wheels for my new Striker (also a 2004 IRS chassis like yours) and will use these just to get it on the road, my plan was then to fit 13" TD Pro-Race 1.2 like you. I had some 13 x 6 Caterham wheels for my old live axle Striker and they just fouled the top of the rear hub by a few mm which I could file off and was hoping the TD wheel would then pop on a treat. I want bigger tyres on the back of my new car so sold the Caterham wheels anyway.

What did you have to do to the lower rear wishbones to get the TD wheels to fit? Also what size and offset wheels did you go for on the rear (and front)? And another thought, what rear bodywork have you got and do your wheels/ tyres 'fill' the arches nicely?

Sorry for all the questions Dave but finding someone that has done exactly what I want to do might mean I don't have to reinvent the wheel (excuse the pun )

[David]

Peter

Had to have the outboard bottom bolt shortened to go inside the 13" wheels (see below) which effectively meant getting new lower wishbones fabricated. Pain, but gave an opportunity to increase set-up possibilities, and there is a MUCH better range of rubber available on 13s than for 14s.

http://img.photobucket.com/albums/v333/ ... ucket3.jpg


ET23 wheels as I was originally going to use the same size tyres all round. I now use 183/55-13 on the front and 215/55-13 on the rear. I have to use 15mm hub-centric spacers to fill the detachable rear arches, but have noticed no negative effects. Photo below shows the car whilst still on ACB10s (sizes were the same, but many clubs banned cross-plies in road-going classes). Penalty of ZZRs (radials) is purely weight; thay are at least as grippy.

HTH


http://img.photobucket.com/albums/v333/ ... ffuser.jpg

[dopdog]

I was looking at doing this on my striker and I am sure someone else on here did it or on locost and had all of the information you would ever need. I think raw do a kit for it as well?

[peter030371]

David, cheers for that, very helpful

Its not just the range of tyres for 13's but also the weight and price are both lower so its win win.

My bottom wishbones have already had a 'mod' done to them so they are non-standard....I guess when I get the wheels I will find out if I can get away with it or if more needs doing.

I have the middle size detachable wings, don't suppose you know what size yours are do you?

[David]

Peter

Sorry, don't know -- but fitting spacers is pretty empirical!

David

[paul2s]

Thanks for all the adVICE …..
Peter Thanks for the calculator will do the sums when I fish out my gearbox ratios
42 Kg wt saving I am sure will be a big help!! I did weigh the seats when I swapped them . They are the intrim narrow seats and they were a little bit heavier than the std bench seats …spose I could take out the passenger seat
David . Good to know that it works OK for an IRS setup, I have spoken to Jeremy at Raw who said they can do the mod…. Did you do yours yourself? The reason I am wanting to do this is mainly for Will who at 19 and only I year driving experience has taken our setup to the limit and is a lot quicker
Than I am ( really annoying also when you are beaten by your son!!)

Dopdog, am I correct in that you ran a supercharged 4age silvertop? It must have been amazing! Its way out of my price range (atm ) did you look at better cams etc option before you did it. ? I have been told that the 16v is easier to uprate than the 20v any thoughts on a cheap option to increase power output?

We just have the one piece rear end.. I suppose that limit’s the width of tyres we can put on the back
I am guessing that having wider rear tyres is more of an advantage for sprints? Does that still apply to the racers?
Is there much of a drop in ground clearance going to the smaller diameter wheels? Still Ok for the road?
Perhaps I was a bit cheeky putting this in the Motorsport section when we are only doing track days!
But we have really got the bug…. Personally I feel as though I have wasted my life!!! only starting this at the venerable age of 55

Cheers Paul

[adithorp]

You don't say (or I've missed it) what size tyres you're currently running; Width and profile not just rim size. 13" wheels/tyres aren't that much different in overall diameter to 15" in profiles commonly used. There's plenty of on-line calculators to help you compare the diameters and speed differences, like this... http://tire-size-conversion.com/tyre-size-calculator/

Saving weight is good especially rotating weight but the best bang/buck when it comes to going faster is to get some instruction.

We really should try and get a few members together on a track day again. I'll post up a suggestion later.