First track day done and dusted

Did my first ever track day on my vfr800 last week and can highly recommend it. Stock standard bike apart from the Leo Vince exhausts, performed really well, managed to keep up with better suited track bikes and especially made up ground under VERY late braking. However, I need some comments from others regarding the back brake. Under heavy braking (I only use the front brake) the back wheel would lock up while changing down. Back in the pits I noticed that the back disc was heavily blued. I know the brakes are linked but is it possible my rear wheel was locking up because I wasnt giving the throttle a big enough blip on the down change, or is the back brake too heavily biased.

 

while you are braking hard, you are only using the front brake lever, this also applies the rear brake as well due to LBS.
The rear tire is unloading due to the late and hard braking, once the tire starts to lift it will lock up.
what you can do is shift your weight farther back and use the rear pedal as well, this will allow you to activate the piston on the front brake that is only used by applying the rear brake.
the only other thing to do is loose the LBS.

 

Thanks for the tip. I didnt realise that a part of the front braking system was only operated by using the rear brake. Does anyone have any idea how much more braking force would be applied by using both sets of brakes?

 

you will have one more piston working on the front and rear.

check and see if these links work for you. they will show you how to de link the brakes using the stock parts.
I also have an extra master that bolts on the left fork if you are interested in buying it to do the mod.

http://vfrworld.com/forums/private.php?do=showpm&pmid=79208


http://vfrworld.com/forums/private.php?do=showpm&pmid=80178

let me know if those links work they seem to go into my mail box for some reason.

If they don't work I will find org post.

 

Thanks for the links but unfortunately they are not working, comes up invalid!

 

ok I will look for org post and put it up here once I'm out of work

 

I doubt LBS is causing your problems, you should have the front preload jacked to help keep weight off the front (to the extent possible) under heavy braking. No need to use back brakes at all while learning the craft.

I suspect the fundamental (and common) issue is downshifting, this may help:
Brake/down - Cornering Forum

and braking technique:
The Fine Art Of Braking - Cornering Forum

 

beta back brakes are already in use due to LBS
I'd also say fork springs and gold valves.

 

I hear ya, but at entry track level riding, 11 times out of 10, it's rider input issues as opposed to mechanical. Everyone wants to blame the bike... its almost always the jockey

 

agreed I myself hated the LBS at first, but just have to re train for the LBS. I like the LBS alot more now.
I will make my final on the LBS after doing a track day.

 

>

Track day (4th) coming up on Sunday. I also brake late in corners but never touch the rear brakes. Yes, my abs is very cool in this situation and allows me to keep up with bikes that are much lighter.

As for the back locking; yes, that has happened to me but not often. The 'hard' blip usually keeps it spinning. My rear disc has no discoloration.

A thought: take it or leave it. An instructor said that my bike (6th gen) can produce a lot of horsepower at different rpms and different throttle openings. He suggested that I get off the red line but stay above the vtec. Then go full throttle to get the hp instead of being around redline and 85-95% throttle. From a few laps of practice, I have gotten faster in the corners because the bike is more manageable. Not as touchy. This also allows for the back wheel to not lock (with a blip of course). Anyway, just a different riding style.

>

 

Bluing of the rear disc just doesnt sound right.......like maybe the one piston on the rear caliper thats being actuated by the front brake is not releasing correctly

 

Thanks for the the input people. I have read the brake/down article and try to do all my braking and down shifting while still upright and releasing the brakes in time to keep up corner speed. As for the throttle blip on the down shift, is it possible on the VFR that I am not giving it a big enough blip. My previous bike was a R6 and though I never used on a track, I did use it hard and never had the same problem with back brake lock up. My main plan is to get smoother laps buy keeping up corner speed and eliminating the likes of the lock up, quicker lap times will come latter.

 

hmmm my 2 cents, I have raced for 4 years and sorry to say I've never " blipped" the throttle on a down shift.
I know all the top guru's write about this and how to do it. IMO unless you are a top 10 pro you time is better spent on working on other things.
what has always worked for me is to keep 2 fingers on the clutch and feather it on the down shift if needed to keep rear wheel chatter in check, sounds to me you are just loading up the front too much and the rear is lifting and causing your problem.
place a zip tie on one of the fork tubes next time you run the bike at the track and see how much ( or how little ) tube you have left, it could be that you are bottoming out the fork, causing the rear to lift as well.
as far as blueing the rear disk, you might want to look into the brake caliper dragging, or you are keeping pressure on the lever and not realizing you are doing this.

by the way what year is the bike you are running??

 

2 PM's sent let me know if you got them or did not get them.

 

Thanks 02 VFR, the PMs came through in my email and photos too. Something for me to read after work tonight. Re the forks, I will try your suggestion. I ran with the std fork preload which seemed fine at the time. Next time will wind it up one notch to see its effect. As for possible drag on the brake: who knows, you may be right that it is just me, so its something else for me to be aware of but I will check it for binding. Bike is a 2008.

 

I ride on the street hard enough to turn my tires blue and run 2 lines showing on fork preload, 150lbs soaking wet.
I also changed my fork oil to a mix so it works out to be 7.5 and added 3 cap full more on each leg, I just dont remember how many cc's I had before adding the 30cc more :doh:

how much do you weigh?

 

173 lbs (but its all muscle). My bike has done 18000km so it would be worth changing the fluids in the not too distant future.

 

might want to bump up to a beefier spring while your at it then, it will help tons on your problem.
The stock spring is only good for feather weights like me LOL
you might want to try the preload all the way in then, but best to get correct springs ( front and rear )for your weight then set sag for you in all of your gear to start.
then you can mess with the settings more once the sag is correct.
if you want to get into suspension more get this book, the best I've read in a long time on the subject.
Sportbike Suspension Tuning, Andrew Trevitt, (9781893618459) Paperback - Barnes & Noble

I also installed a 19mm tail riser and raised my fork tubes up 3/8" for faster turn in. Something you can mess with in the future as well.