brakes
Author
Discussion

dilley

Original Poster:

205 posts

233 months

Sunday 17th June 2007
quotequote all
I have noticed that It is very very hard to apply the brakes even at speed, (I know they are never going to feel like servo brakes) it feels as if I need to add more to the front and less to the rear, is this possible on the bias bar?? I had the same problem on my "7" this had a break proportioning valve on the rear but I only had 1 master cylinder.

GTWayne

4,595 posts

246 months

Sunday 17th June 2007
quotequote all
dilley said:
I have noticed that It is very very hard to apply the brakes even at speed, (I know they are never going to feel like servo brakes) it feels as if I need to add more to the front and less to the rear, is this possible on the bias bar?? I had the same problem on my "7" this had a break proportioning valve on the rear but I only had 1 master cylinder.
Yes, it is possible to alter the brake bias. I have a remote adjuster and a readout on my dash so that I can see at a glance what the percentage is front/back; Of course it is possible to do it manually but the former is much easier. I am far more used to power assisted brakes than not and did find the non assisted AP's took a bit of getting used to. Don't forget that you are used to your 7 which is half of the weight.
Just reading P's post on Kumho's and remembered that I have locked the wheels a few times now and so it would appear that the tyres are the limiting factor with regards to being able to stop any quicker now, but I am working on that wink

dilley

Original Poster:

205 posts

233 months

Sunday 17th June 2007
quotequote all
how about toyo r888's??

GTWayne

4,595 posts

246 months

Sunday 17th June 2007
quotequote all
I have a set of these on my T5 Volvo estate and am well impressed I must say. I have also ordered a set for the Ultima for my Spa trip but although the correct size is available for the rear, there is no direct replacement for the front and so I will be trying a 225/40 X 18 which is taller by approx. 4mm but I really can't see it being a problem.

dilley

Original Poster:

205 posts

233 months

Sunday 17th June 2007
quotequote all
I believe that a higher profile all round would help handling on the road.

What price are the toyo's??

dilley

Original Poster:

205 posts

233 months

Sunday 17th June 2007
quotequote all
straying a bit here.....

wayne, what speeds are you getting in each gear with your ratio's?? I'm trying to work out the best combination.

GTWayne

4,595 posts

246 months

Sunday 17th June 2007
quotequote all

I am using a G50/03 and I have a 3.444 CWP and shift @7200 RPM
1st 2.176 = 74.1 mph
2nd 1.579 = 102.1 mph
3rd 1.174 = 137.3 mph
4th 0.923 = 174.6 mph
5th 0.756 = 213.2 mph

IMO a six speed gearbox is a waste of time on these engines and whilst I appreciate that most builders find themselves in a position where whatever comes along first gets used, I really do think that this is one aspect of the overall package that gets overlooked. I spent a long time getting this gearbox together and can not stress highly enough how much of a difference a proper gearset makes across the board to overall performance not to mention drive ability and comfort.
Not what you want you hear I know but have you considered obtaining a 5 speed box, modifying it and swapping it over? At least you will be able to sell the 6 speed on and may even make a little on it depending on what you can find a G50 for? Worth a thought at least.

andygtt

8,345 posts

293 months

Sunday 17th June 2007
quotequote all
GTWayne said:
I am using a G50/03 and I have a 3.444 CWP and shift @7200 RPM
1st 2.176 = 74.1 mph
2nd 1.579 = 102.1 mph
3rd 1.174 = 137.3 mph
4th 0.923 = 174.6 mph
5th 0.756 = 213.2 mph

IMO a six speed gearbox is a waste of time on these engines and whilst I appreciate that most builders find themselves in a position where whatever comes along first gets used, I really do think that this is one aspect of the overall package that gets overlooked. I spent a long time getting this gearbox together and can not stress highly enough how much of a difference a proper gearset makes across the board to overall performance not to mention drive ability and comfort.
Not what you want you hear I know but have you considered obtaining a 5 speed box, modifying it and swapping it over? At least you will be able to sell the 6 speed on and may even make a little on it depending on what you can find a G50 for? Worth a thought at least.
I absolutelly agree, and the gearbox is one of the most important part of the package IMO...
You can get the gearing to work on a 6 speed which is what I am doing, but its very unlikelly a CWP change will acheive this as most G50's and I beleive Getrags come with the best one (i.e 3.44).

What I have done is bought another box and I am picking the ratio's from each... but again it's not that simple as only certain ratio's can be swopped (ie 3rd with 4th, 5th with 6th.

For information mine is useing a 3.444 CWP and shift at 6800rpm and larger tyres.
1st 3.154 = 53mph
2nd 2.000 = 84mph
3rd 1.410 = 118mph
4th 1.120 = 149mph
5th 0.970 = 172mph
6th 0.750 = 223mph (may replace with a new 0.656 and swop 5th for a 0.857 i have)

It's a big ask to get the ideal rations from a Getrag, you may end up spending a fortune for small changes on a box that is weaker than a G50 anyhow.

andygtt

8,345 posts

293 months

Sunday 17th June 2007
quotequote all
Sorry to elaborate on how to choose the in between gears you need to look at the drop in RPM when you change up.
So in Waynes example assuming he changes at 7200rom his drop in each change is:
1st - 2nd = 1975rpm
2nd - 3rd = 1847rpm
3rd - 4th = 1539rpm
4th - 5th = 1303rpm

pretty much spot on IMO

GTWayne

4,595 posts

246 months

Sunday 17th June 2007
quotequote all
^ Exactly right for MY application Andy. With peak power of 650bhp @ 6400rpm and peak torque of 611 lbsft @ 4800 this gearset came out favourite every time when Chris Fischer ( who has long since left PHII ) and I crunched the numbers back in 2001 eek was it really all that long ago?

ultimad

315 posts

255 months

Sunday 17th June 2007
quotequote all
andygtt said:
You can get the gearing to work on a 6 speed which is what I am doing, but its very unlikelly a CWP change will acheive this as most G50's and I beleive Getrags come with the best one (i.e 3.44).
Andy, in my ignorance can you explain why another CWP is unlkely to improve the Getrag and why 3.44 is best for it ? Say if there was an alternative that made the gears taller, what would be wrong with that ?

andygtt

8,345 posts

293 months

Sunday 17th June 2007
quotequote all
Well a 3.444 is usually the lowest you can get, and thus the best for raising the top speed in gears.... thus a change to an available CWP is more likelly to lower the ratios (as porsche race cars want to lower the ratios as the engines rev higher).
Of cause a bespoke lower one may be possible but it's going to be expensive and the getrag isn't as strong as the G50 so might be risky.