Downshifting / Brake Bias Unbalance
 

Hello Guys,

I need advices, there not a lot of cup cars owners in my Area and i feel like i have to ask

I have done about 15 hours of private track days on my new to me Cup car from last year. It is a 2008 997.1 cup, No Abs, No paddle shift

There is a struggle i have and it is related to downshifting and brake bias and it reduce my confidence...Especially coming under hard braking to a hairpin..

Brake Bias :
For now, i have ajusted brake balance so the rear wheel are just about to lock under hard braking with engine brake. So i need engine brake to have full braking power.
I do not know if it is right, but if i add more bias to to rears, they lock more often under hard braking with engine brake.

Downshifting :
When downshifting two gears under hard braking, i let go of the clutch between gears, smooth but fast. But still upsets the car a bit.

I feel like the combination of the twos upsets the car and i have spun the car twice (with no damage) entering a hairpin under hard braking and doing little trail braking. I feel like i lose the rear easy.

I now do all the braking/downshifting straight but bit early...has had a effect on my confidence and now i don't want to trail brake even a bit ...I know i'm loosing momentum and it is not the optimal way to do it.

What am i doing wrong ?

Downshifting:

Good reason to share one of my favourite 'paddle dance' video's. This talented tap dancer shows how to heel and toe like no other.
Only then you can avoid the clutch to unsettle the car by matching the gearbox revs to the engine.

The cheapest alternative to this is a throttle blipper. It's a metal bar connecting your gas pedal to the gear lever and automatically 'blips' the throttle on downshift.
Most 997 Cups had them installed and later a lot of cars were upgraded to paddle shift (KMP, Holinger, Megaline)

https://cimg3.ibsrv.net/gimg/rennlis...97b192067d.jpg

You should not be braking with the engine - period. Your downshifting should also not affect your braking. The cheapest and most rapid way to figure out what to do is to hire a professional coach that is familiar with the 997.1 Cup platform.

I'd get the blipper stick... Plus you beat the crap out of R&P and synchro's without a blip.

Just my 2cents, but you want fronts to lock up before rears so car stays in straight line.

Definitely use the brakes to stop the car and downshift as late as possible before the corner entry to get the car in the proper gear for corner exit. Somebody said "a good downshift needs to be heard but not felt" or something to that effect. If you're upsetting the rear of the car in dry conditions, imagine if it was wet... I made a video of myself below a while ago to "study" my own downshifting process and improve it as much as possible. Hope it helps:


MGR

Thank you for the input, first video is great.
I do have an autoblip mechanical rod.
The gearbox functions perfect and has just been rebuilded.. i think its just me banging down the gears too late in the braking sequence.
Can't really compare that to driving a street GT3 on the track...no t/c, no abs, no powerbrakes and brake bias changes depending on temperatures.
You learn all the time

If you feel shifting was the cause of your spins I don't understand why you need to avoid trailbraking. I have the same car. 2006 with Giggle stick and no ABS. Typically I downshift just before turn in (often 2 gears with one clutch release). I don't find I need to downshift between turn in and the apex. Why add the risk if there is no benefit. This allows more opportunity to focus on varying the rate and timing of your brake release. Early in learning how to modulate the non-assisted brakes, my brake release was too abrupt in lower speed corners. Combined with larger steering inputs, this can cause snap oversteer. I've improved my brake release and no longer have that issue.

Another thing that has helped is installing brake pressure sensors. Brake pressure can be displayed on the Motec dash. Before going on track I'll practice braking while the car is warming up to remind myself of the forces using the pressure display. A motec shift light module can also be programmed to display braking while on track. Both have helped tremendously speed up the learning curve for me.

Great cars and tremendous fun once you get the feel for them.