Another gearing question...

[Shiftone]

I'm just getting into Oval racing and was trying to get my head round gearing choices.

I run brushless 13.5 blinky 1S.

After a few weeks of getting use to my car and racing, I'm using a 45/16 gearing for a rollout of about 54.7mm/rev

My question is how does total tooth count effect the car when rollout remains similar? For example if I use 51/18 for a rollout of 54.4mm/rev - aside from being a fraction slower what are the repercussions?

Thanks in advance.

[LongRat]

Larger diameter gears for the same (rough) overall ratio will:

1. Wear more slowly (not a concern)
2. Accelerate and brake slightly worse due to increased rotating mass
3. Position your motor further from your axle, changing the fore-aft weight balance of the chassis and will reduce the effective unsprung mass on the pod.

[Shiftone]

What would you say is preferable in oval? Larger or smaller gears?

I did notice my car had a greater perpencity to spinning out from the rear when accelerating with the 45T. Would going to a larger gear set with a similar ratio help to alleviate that problem?

[LongRat]

I don't race oval, so have no direct experience. But without knowing the rest of your set up I don't think anyone could give you a good answer to that really. The shifting forward of the motor weight with larger gears is probably the strongest effect. Try using softer rear springs to compensate.

[Shiftone]

Thanks for your advice.

I was using a 48 spur recently which sat the motor forward a bit - so going down to the 45 and moving the motor back may account for some of the handling changes I noticed last race night.

I run Contacts, 50mm 35s on the back and 46mm 50s on the front - but have a pair of 32s coming for the rear.

I am also running the blue powder coated rears so definitely could go lighter on them too.

The setup is an alloy chassis with F1 style WBs mounted directly to the chassis with a fair amount of washers to set the camber, castor and ride height. I basically built them up to the same height that I was using with the standard WBs but with the added camber from the 3rd mounting hole.

I run zero toe and about 4mm ride height slightly lower to the front end.

Powered by a Trackstar One Cell ESC and 13.5T on 1S Lipo. Solid rear axle.

Ginetta shell and diffuser.

In your experience is it best to find a spur gear that works well and stick with it - changing the pinion to keep the rollout as the tyres wear down?

[SlowOne]

Gonna slightly disagree with Long Rat here...

Larger gears less wear (but you'll never notice!)

Larger gears mean more tooth engagement so more efficient transfer of power (but you'll never notice)

Larger gears will add rotating weight, but as a proportion of the total rotation weight of the rotor, axle, wheels and bearings... you'll never notice!

Shifting the motor weight forward makes little difference to the weight distribution as all the weight of the pod goes through the front ball joint of the pod. However, it will make a difference to the way the car turns. The further back the motor the more weight over the axle and more that weight will swing when the car turns.

Using a larger spur and moving the motor forward would make the rear swing less, giving you the effect you describe. This is the biggest effect of motor movement in pan cars - remember they are the only race chassis in the world with a hinge in the middle!!

If you are so close to the edge with you car's handling that moving a motor a few millimetres forwards changes the handling significantly, the as Long Rat says you need to look at your set-up compared to others in your club with the same car. HTH

[SlowOne]

Yes, choose a spur and stick to changing pinions as the tyres wear - most do that.

If you are running 35s and everyone else is running 32s, that's the more likely explanation for the back losing grip in the turns.

I don't run Oval, but having the front lower than the rear will promote oversteer. Is that the usual setup the fast guys use at your club? When in doubt, put the common settings everyone else uses on your car and then try the differences you find between the top drivers. Start from there to try things, only ever changing one thing at a time.

Compare everything you do to the lap times you run. You are interested in your fastest lap time, but more interested in the difference between your fastest lap time and your average lap time over the race. Look at the top drivers 'difference'.

In 12th, the top drivers have a 'difference' of about 0.2 secs between their fastest lap time and their race average lap time. Look at the top drivers in your club - what is their difference and what is yours?

When you make any changes to the car look at that difference as well as your fastest lap. Yes, you need a fast car, but you also need a car you can drive very consistently over the five-minute race. Some changes will make the car fast over one lap, and some will make the car more consistent. You need both!! HTH

[Shiftone]

More good advice thanks.

I've been getting print outs of my better runs and looking at both my fastest and average laps when taking the badly driven laps out of the equation.

I'm only about 4 weeks into my racing career so still learning a lot both in terms of driving and set up. Week before last I set myself a target of getting my lap average consistently under 5 and this week achieved that - even with the handling issues. I think average was about 4.5 and fastest was 4.08.

The fast guys at my club are probably a second quicker than that per lap so that's what I'm aiming for. Every week they get a little more cagey about their set ups lol.

My next goal is to get my total laps up into the 70s - the fast guys are putting down 78-83 laps.

The fastest my car has ever made it round was 3.95 so I think there is still room to get my setup dialled in.

Back to gearing - as this is something I want to get settled before making finer adjustments to springs etc - looking at some ratio charts I've made there is often a gap in the rollout as the tyres wear down. As in at say 47mm rear dia a 16T pinion drops bellow my target rollout of say 53-54 and a 17T over shoots it. How do people usually deal with that?

I've looked into 48DP gears and they seem to not have this problem.

[MrTross]

48/20 I was told for my local club Hot's as I'm just going over to brushless