Ive been making some enquiries into getting a recon diff and have come across the question of which ratio i should buy.

Im told that 3.38 is the one to have for BEC's

Is this right?

Cheers

Very much depends on the wheel / tyre size you are running. I had a 3.62 LSD with 185/60/14 which would hit the limiter at 130. Going beyond 130 and you will need to do something about the aerodynamics as this becomes the limiting factor on sevenesque cars.

I've just fitted a 3.38 lsd to my phoenix to compensate for the lower profile 195/55/14 tyres and am waiting to see if will still hit the limiter in top with such enthusiasm.

Cheers

Jim

[Edited on 24/3/04 by jimgiblett]

Im planning on using 17" wheels. ANyine know what diff this will make.

Cheers

im using a 3.6something diff and 205/40 17's and the R1 engine iv had 120 out of it so far with about 500 rpm left,im not sure if my speedo is right though,,in top gear its about 11 mph per 1000rpm

[Edited on 24/3/04 by OX]

Chris, it depends on what profile tyres you are going for, its all about the actual rolling radius rather than the wheel size itself.

Put your tyre size and engine etc into this spreadsheet and see what comes out.

BTW why 17"s? Ive never tried a Seven type car with wheels that big on but compared to smaller wheels its not meant to be too healthy for the handling.

Chris

[Edited on 24/3/04 by ChrisGamlin]

I just think its a set of alloys that make a car look the part, and a nice set of shiny 17"s will look the biz on a kit. Besides so many others have them. I know its gonna make the car harder, and maybe a bit skitish on corners, but unless anyone can convince me otherwise, 17"s its gonna be.

Had 15"s on my quantum, and i thought i looked like they need to be bigger.

Every inch counts!

Fair enough, I think 15s look good but have seen a few Dax cars with 17s on and its a bit OTT for my taste, but back to the performance issue, without comparing both on the same car its hard to judge how much difference it makes. Theoretically tho, its the weight as much as anything that causes the problems. 17"s are significantly heavier so add to the static weight, you can get a good 13" wheel tyre combo under 10kgs a corner, but I bet you'll struggle to get below 15-17kgs with 17s, so thats at least 20kg added to the car straight away. Also it adds more rotating mass which is harder to change direction when steering the front wheels, again all theory but it makes sense.

cheers

Chris

quote:

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I've just fitted a 3.38 lsd to my phoenix to compensate for the lower profile 195/55/14 tyres

---

Probably converted a 3.62 LSD with a 3.38 CWP, I know thats what a friend with a Megablade is doing

13/15" or 17"????

Depends on what's more important to you, looks or handling......personally it's handling all the time for me.

What size are your wheels chris g and where did you get them ???

No 3.38 comes from 2.0 auto sierra (early carbed versions).

I combined a 3.38 open and a 3.62 LSD. I was going to have a go at the conversion myself but ended up taking it down to Road and Race in Shoreham. They put the LSD unit into the 3.38 rather than change the CWP as this makes it a fairly quick job.

Cheers

Jim


"3.38 IIRC is from a Granada 2.0, right?
How does it have LSD? Have you converted it? "

[Edited on 29/3/04 by jimgiblett]

Mine are 13"x6" Compomotive ML 3 piece split rims, got them from George Polley. You can get similar in a one piece for a fair bit less cash, although not as light (mine are about 4kgs)

I've got a 3:38 diff on 17's. I can't comment on how well the 13's handle but im very happy with how stable the car is, and the ride is good but then I have got some cobra 7's

My 3:38 came from an xr4x4 german import

Going back to the big wheel / small wheel debate, one other thing that wasnt mentioned is the available tyres in each size.
Firstly 17s are usually substantially more expensive for quality tyres, and secondly virtually all 17" tyres will be designed for much heavier cars so use much harder compounds. You'll probably never get real heat into a tyre like that so arent going to generate nearly as much grip compared to a nice sticky Yoko 021/032 or Avon ACB10 13"/15" tyre specifically designed for lighter cars like ours.

Chris

Chris, Got some heat into those rear tyre's yesterday, the back end was very hot, power slides and that ;-)

LOL, you're meant to be able to generate heat without resorting to burnouts tho

WHY, Its miles more fun when your at the lights and 3 lads are in a Bmw M5 all staring, lights go green the m5 shoots off you give it to much revs, light up the rear tyre's they catch some grip and it soon becomes a small m5 in the rear Mirror :-)

I felt a prat at the next light when they turned green, I stalled it. the M5 dissapeared

Now whats going to last the longest Tyre's or license

so do you really drive fast anough to use your Yoko 021/032 or Avon ACB10 13"/15" tyres on the road ,for track use yes and i would love some but i drove back from northwich yesterday way over the speed limit and way to fast for the roads but the car stuck to the road ok and the tyres are as cheap as they come ,with 18 psi in my tyres they do get some heat in them .

Yup point taken, the only time you'll really get heat into any tyres are on track and my use of those tyres is geared towards track use and the best handling I can muster hence going for the 13" wheels and sticky tyres. For 90% of road use you wont really need the extra grip for cornering I guess (cos you cant push to those limits on the road!), but I still think any lightweght BEC whether it be on road or track would still ultimately benefit from having stickier rubber and the light wheel / tyre combinations that a large wheel cant provide, not just for accelerating and cornering but for stopping too.
However I dont wanna stir up anything here as everyone has different priorities in what they want their car to be, so everyone's choices will be different

havnt seen many cars in the flesh but its cool how they all have there subtle differences

Yup, its one of the good things about a kit car when compared to something like a Caterham, which are all identical and if you change them from that they lose value. Its nice to be able to build the car to how you want it to be rather than how a manufacturer says it should be.
I guess its bad in some ways too cos there will always be the odd monstrosity out there to be aware of when buying!

Chris