Changing Final Drive any downsides?
Discussion
Thinking of changing the final drive in my Clio 172 tack\race car. Gearbox is coming out (for a leak) so fitting an LSD and maybe a shorter FD while it's out.
Looking at a Bacci 12\58 which will give a top speed of 131 in 5th (only ever reached 115 top speed in any race).
Any downsides that I won't be aware off?
Not too experienced , started 18 mths ago (couple of kart\car track days before this) with a std 172 cup (now stripped and race prepared) and have completed 3 races this year, Brands, Mallory & Donington.
Thanks....
Looking at a Bacci 12\58 which will give a top speed of 131 in 5th (only ever reached 115 top speed in any race).
Any downsides that I won't be aware off?
Not too experienced , started 18 mths ago (couple of kart\car track days before this) with a std 172 cup (now stripped and race prepared) and have completed 3 races this year, Brands, Mallory & Donington.
Thanks....
Here are my proposed changes -
and this is the std FD ratio
At the moment I've never used 1st (apart from the start) 2nd - most hairpins (Mallory), never at brands or Donington.
A lap of brand is 4th for paddock - 3rd for druids - fourth along Copper straight, 3rd goind into clear ways and the 4th just after the exit and 5th just passed the start finish line....
All fairly comfortable I'd say myself.
300bhp/ton said:
You might want to check terminal speeds in gear and see how it affects it. Overall I'd have thought it'd be good, but you might create a few flat spots. It will mean more gear changes and you need a driving style to suit i.e. spending more time in the higher revs.
Terminal speed seem to be ok --130 as at the moment I've never got much past 115 - maybe 120 on the back straight at Snetterton..Trying to work out my Brands gear changes now...will have to watch a lap and note the revs speed of each change and & adjust with the ne FD ratio - crude but should give an idea.
Krikkit said:
Also worth thinking about what kind of diff you're using if it's getting pulled to bits - a plate is a significant upgrade from an ATB/Quaife type.
The only thing putting me off the plate diff is the maintenance - I can't get the box out myself (would have to pay to get it removed) and not too sure of the cost of the yearly strip & re-plating. Guessing that would be at least 2-£300 plus the £150 to remove - refit the box.Not sold on the ATB - yet, though I've got an option on a 1 year old one, been used in 4 races, in the pipe line. This may be the deciding factor (cost and maintenance) for an LSD...It'll be an improvement over the open STD one fitted at the moment.
Kozy said:
A lot of people seem to get suckered into the marketing with shorter gears, the sales pitch along the lines of "20% more torque to the wheels" is technically correct, but also misleading. If it were 20% more torque at the same speeds then yes it would be significantly quicker, but gearing just scales the engine output, so what you actually get is 20% more torque at 20% less speed. If you did that on the engine's torque curve, the power output would remain unchanged.
The net outcome is that while the peak acceleration in each gear is higher, it's delivered at proportionally lower speeds and the overall acceleration of the car is not altered greatly. It will have a slight improvement, but if the change in ratio suggests that you'll gain 20%, it will nowhere near modifying the engine to deliver 20% more torque.
If you are looking to improve laptimes, I'm not sure it represents a good value modification over engine tuning. The LSD however, definitely does.
Good point....The net outcome is that while the peak acceleration in each gear is higher, it's delivered at proportionally lower speeds and the overall acceleration of the car is not altered greatly. It will have a slight improvement, but if the change in ratio suggests that you'll gain 20%, it will nowhere near modifying the engine to deliver 20% more torque.
If you are looking to improve laptimes, I'm not sure it represents a good value modification over engine tuning. The LSD however, definitely does.
Will have to get my lap of Brands and work out the where the "new" gear changes will be, I'll do that for Mallory and Donington too.. theoretically - I'm thinking 3rd would be 4th...maybe not as easy as that....as I won't know where the 7400 rev limit will be with a shorter FD.
How can I get time distance on the two rpm - speed graphs I posted above?
Kozy said:
Actually thinking about it, the gearing could be related to the distance without all the other stuff, so you could probably figure out shift points around a track, however I should imagine this would end up being incredibly complex and time consuming for little real benefit.
How much does the FD cost, and how much could you do to the engine for the same money?
Around £650, thinking of using Bacci...How much does the FD cost, and how much could you do to the engine for the same money?
http://www.bacciromano.com/index.php?p=prodotti&am...
Euro 1.24 for a £1...
The Clio F4R is and expensive lump to get any worth while gains out off....ITB's are around 2.8K with full management & fitted - for 20-25BHP.....
Any idea how to estimate how quicker the 7400 limit would be reached with a shorter FD..
Kozy said:
Going down a wheel size would have similar effects yes. The effects on RPM and acceleration are probably not as pronounced as a ratio change, but there are more benefits, less unsprung and rotating mass (by far and away the best place to lose weight), smaller, lighter, cheaper tyres etc.
My point is though that personally I would not spend money on gearing that could be spent on improving the engines output unless the car was significantly over or undergeared, which I don't believe a Clio is. Mods like this are great at making the car feel faster, but it's largely placebo with a near stock engine.
I have a set of catcams 438 - which has a gain of 15-20bhp - so near 190-195 and 875kg dry.My point is though that personally I would not spend money on gearing that could be spent on improving the engines output unless the car was significantly over or undergeared, which I don't believe a Clio is. Mods like this are great at making the car feel faster, but it's largely placebo with a near stock engine.
Krikkit said:
The annual/two year maintenance shouldn't be too costly, a chap I know runs a gripper plate in his Peugeot and a service was about £150 with some upgraded pins and bits of pieces to bring it up to current spec. But the costs spiral if you can't get the box out yourself etc.
If you don't want a plate, then you at least need an ATB. The difference in lap-times just from adding that will be significant, and a plate is almost the same amount again...
Bought the quaife today - a lot cheaper than new. Also after working out the time\expense of a gripper decided to go for the ATB - still to decide on the FD though.If you don't want a plate, then you at least need an ATB. The difference in lap-times just from adding that will be significant, and a plate is almost the same amount again...
Received a reply from the FD manufacturer this morning - the 25% discount offered brings the price down to £579 (inc 20% vat), Not sure of the fitment of the crown wheel now that they have offered two choices and I have a Quaife to fit - can any one offer advice in this respect?
The price quoted earlier £644 wasn't including VAT either so quite a saving I've been offered.
Dear Peter,
the final drive ratios can be supplied in about 10 days from the order.
If you couple it with the original gearbox, the pinion is fully compatible with the original one (same layout).
Normally the crown wheel is supplied bolted-type (for our DA016 LSD) for racing use and you can adapt the original differential with it with easy modifications.
But if you need a pressure-type crown wheel (as the original layout), we can produce it for you in the same time production of the pinion.
25% discount was a July and August offer.
35% discount is for orders placed in the Koeln Iternational Expo (next week).
But if you confirm me the order and the payment is placed before the end of november, i can give to you the 25% offer in any case.
Thanks and regards,
Giulio Dialti
Original Message ----- From:
> - Your message: Hi, I'm looking at a final drive ratio of either 12/56 to 12\59, for my Renault clio 172 Cup with a JC5 gearbox...
>
> Will your final drive fit this gear box with no other modification? The bearings\needle rollers are the same/
>
> Also you had a price discount of 25% -35% (got an email earlier) can i also have a discount applied too?
>
> Thanks
The price quoted earlier £644 wasn't including VAT either so quite a saving I've been offered.
Dear Peter,
the final drive ratios can be supplied in about 10 days from the order.
If you couple it with the original gearbox, the pinion is fully compatible with the original one (same layout).
Normally the crown wheel is supplied bolted-type (for our DA016 LSD) for racing use and you can adapt the original differential with it with easy modifications.
But if you need a pressure-type crown wheel (as the original layout), we can produce it for you in the same time production of the pinion.
25% discount was a July and August offer.
35% discount is for orders placed in the Koeln Iternational Expo (next week).
But if you confirm me the order and the payment is placed before the end of november, i can give to you the 25% offer in any case.
Thanks and regards,
Giulio Dialti
Original Message ----- From:
> - Your message: Hi, I'm looking at a final drive ratio of either 12/56 to 12\59, for my Renault clio 172 Cup with a JC5 gearbox...
>
> Will your final drive fit this gear box with no other modification? The bearings\needle rollers are the same/
>
> Also you had a price discount of 25% -35% (got an email earlier) can i also have a discount applied too?
>
> Thanks
davepoth said:
Given that you aren't using 1st gear at all for racing, it might be more worthwhile looking at a closer ratio gearset, although I have no idea of the relative prices.
I did look into this, dog, straight cut and to replace the gear set would be around 2-3k. Take it you mean something like the top 2 gear sets on this page? http://www.bacciromano.com/index.php?p=prodotti&am...Not sure If I want to spend that amount though would be of great benefit...
Kozy said:
In what gear, from what speed, going uphill or downhill? It wouldn't really mean much TBH.
If, as you say, further power upgrades are prohibitively expensive then the FD might be worthwhile, but it really is down to luck as to whether it benefits you more than it hinders you. If I couldn't find anything better to spend the money on I would probably just stick it in the pot towards consumables/testing/entry fees etc.
Yes good advice!! - changing the FD isn't as straight forward as I'd thought - will still try and work out, in a rough form the new gear changes on track first.If, as you say, further power upgrades are prohibitively expensive then the FD might be worthwhile, but it really is down to luck as to whether it benefits you more than it hinders you. If I couldn't find anything better to spend the money on I would probably just stick it in the pot towards consumables/testing/entry fees etc.
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