Low Side at Brands - Third Track day in a row!!

[Kiwi_uk]

A couple of months back I lowsided coming out of Barn at Cadwell. At first we thought the issue was with the 2CT tyres I was using giving no feedback and just letting go. First time on these tyres was at Cadwell but I doubted this to be the problem as my skill levels do not match the capabilities of the tyres or bike and I was not snatching at the brakes or accelerating practically hard. Over all I felt smooth and well within my limits. Ignored advice and decided to stay on 2CT for track day at Folembray France two weeks later. Again I low sided (this time with only ten minutes of the day to run) coming out of the first chicane. I was instructing on the circuit in the morning so was only riding at 50% and didn't really start to move things on until the later part of the afternoon.

Thinking I'm an idiot for not listening to advice and my wife walking away in disgust (two crashes in two weeks) I decided to change my tyres for the Brands track day a couple of weeks ago. Well guess what happened in the third session at Brands, yes I low sided again tipping into Surtees. No brakes and on positive throttle. You normally know when you're pushing it to hard as you start to have OH SH!T! moments. No feed back at all and no warning. WTF!!

Well yesterday I returned to Brands with my bike in an attempt to try and resolve the problem. This is the third low side in three track days running different tyres and in places you wouldn't normally low side so this was starting to do my head in.

Forks were taken out and sent to the guy who does my suspension to strip down and make sure there's nothing wrong. Forks returned with the all clear. Next thing to look at was the brakes, stripped down callipers and serviced. Again nothing found that would cause them to bind.

Organised for my suspension guy to ride my bike at Brands and try and see where the problem might be. If he finds nothing then it must be pilot error. He jumps on Factory for 4 fourth session and comes in after 5 minutes. Front brake binding was the call. Threw bike on to paddock stands and tried to spin front wheel, only half a turn!! Turns out the after market levers I use were pushing on the piston in the MC enough for the pads to sit against the discs. When they heat up they expand causing the front wheel to lock when transitioning from brakes to power (not the normal place to low side). We whipped out the brake lever, filed 1 - 2 mm off a lug that presses against the piston. Back out in next session and problem solved!!!

Proof is now in the pudding, I have four days in Cartagena, Spain in December which is when I get the test her out again. Fingers crossed this is the problem for all three crashes.

Anyone else going to Cartagena in December? http://www.focusedevents.com/event_list.asp?event_... £549 including flights, accommodation, share of rental car, 4 days on track and bike transported down. Bargain!!! Chilli's going!!

[podman]

Bloody hell...dunno if your lucky or un lucky...

name and shame the manufacturer of the levers ...have you contacted them yet?

[Busamav]

Kiwi_uk said:

Turns out the after market levers I use were pushing on the piston in the MC enough for the pads to sit against the discs. When they heat up they expand causing the front wheel to lock when transitioning from brakes to power (not the normal place to low side).!

Thats the 4th instance i have heard of that involving aftermarket levers .

2 cases involved Busas going down in a straight line whilst at RAF Woodbridge doing top speed flyers, the last instance was last week on the A4 , a guy on an R1 felt his front wheel nip up just in time

[Chilli]

Hello mate,

Sooooo glad you've got to the bottom of it. Wouldn't the bike want to sit up braking though, and have the opposite effect? Well, obviously not, but would be interested if someone could explain the physics!

How's "The Drive" treating you?

ps - Anyone fancy that trip to Spain. Corking track, fantastic weather, and I'll chuck in a bit of on-track tuition if you like???!!!!

[Hooli]

Chilli said:

Hello mate,

Sooooo glad you've got to the bottom of it. Wouldn't the bike want to sit up braking though, and have the opposite effect? Well, obviously not, but would be interested if someone could explain the physics!

How's "The Drive" treating you?

ps - Anyone fancy that trip to Spain. Corking track, fantastic weather, and I'll chuck in a bit of on-track tuition if you like???!!!!

it will try to sit up unless the braking effect causes too much tyre slip against the lateral load. so going even slower it may stand up a bit, load it up a touch & it just slides.

[hornetrider]

Mate that is bad news. I see you have an Aprilia. I had the same problem with my Falco (though I didn't crash it), I noticed the aftermarket levers were binding and filed off an excess to allow the levers to return fully to their original position.

Another member of ridersite has noticed this as well. You didn't get the levers off the bay did you? We did...

[shot2bits]

Sorry to hear about all your troubles - must be great to know what's finally going on

I low sided my GSXR last year at Snetterton - no idea why either and I was on 2CT's but that's not the cause of your issues as you've found out.

That £549 offer with Focused is fantastic value - so tempted...

[Chilli]

shot2bits said:

Sorry to hear about all your troubles - must be great to know what's finally going on

I low sided my GSXR last year at Snetterton - no idea why either and I was on 2CT's but that's not the cause of your issues as you've found out.

That £549 offer with Focused is fantastic value - so tempted...

Go on.....you know it makes sense! At least 20 degrees, guaranteed dry sunny conditions....Oh, I think I've just.....

[Steve_T]

hornetrider said:

Mate that is bad news. I see you have an Aprilia. I had the same problem with my Falco (though I didn't crash it), I noticed the aftermarket levers were binding and filed off an excess to allow the levers to return fully to their original position.

Another member of ridersite has noticed this as well. You didn't get the levers off the bay did you? We did...

I spoke to the mechanic at the dealer I use for spares my Aprilia a while back and he mentioned something that may be relevant. I'm going from memory here, but I recall there's a means of adjusting part of the plunger assembly, which allows you to vary the span (this is on standard levers). If you over adjust things then you can block the return for the master cyl, which as the brake fluid expands when it gets hot, means your brakes stay on. Your problem sounds like it was different, but thought this info might be of use for future reference. I have a Brembo radial master on its way from Bike Torque Racing and from what you're saying it might perhaps be worth running the problem you mention past them first, before I put myself at risk.

Steve.

[GreenV8S]

Steve_T said:

If you over adjust things then you can block the return for the master cyl, which as the brake fluid expands when it gets hot, means your brakes stay on.

That's exactly what causes this problem on cars, and I imagine the bike brakes work the same. The brake circuit is supposed to be connected to the reservoir at rest, but the first fraction of an inch of travel on the master cylinder closes this port off and converts it to a closed circuit. If the master cylinder is mechanically prevented from coming back that last bit, the brakes work as normal but the circuit doesn't get opened to the reservoir. As soon as you get any heat in it, thermal expansion causes pressure to build up and apply the brakes, causing more heat and so on.

[Kiwi_uk]

Steve_T said:

hornetrider said:

Mate that is bad news. I see you have an Aprilia. I had the same problem with my Falco (though I didn't crash it), I noticed the aftermarket levers were binding and filed off an excess to allow the levers to return fully to their original position.

Another member of ridersite has noticed this as well. You didn't get the levers off the bay did you? We did...

I spoke to the mechanic at the dealer I use for spares my Aprilia a while back and he mentioned something that may be relevant. I'm going from memory here, but I recall there's a means of adjusting part of the plunger assembly, which allows you to vary the span (this is on standard levers). If you over adjust things then you can block the return for the master cyl, which as the brake fluid expands when it gets hot, means your brakes stay on. Your problem sounds like it was different, but thought this info might be of use for future reference. I have a Brembo radial master on its way from Bike Torque Racing and from what you're saying it might perhaps be worth running the problem you mention past them first, before I put myself at risk.

Steve.

Hi Steve, this is pretty much my problem however there was not enough adjustment on the plunger assembly. (So that's what it's called )

[Kiwi_uk]

hornetrider said:

Mate that is bad news. I see you have an Aprilia. I had the same problem with my Falco (though I didn't crash it), I noticed the aftermarket levers were binding and filed off an excess to allow the levers to return fully to their original position.

Another member of ridersite has noticed this as well. You didn't get the levers off the bay did you? We did...

The levers are Pazzo shorties. You actually use the plunger bit from the original levers which is what we had to file down. The levers are great and I would not trade them for anything else. If I new a little bit more about this sort of problem then I could have avoided it.

Edited by Kiwi_uk on Wednesday 10th October 11:14

[Steve_T]

Kiwi_uk said:

hornetrider said:

Mate that is bad news. I see you have an Aprilia. I had the same problem with my Falco (though I didn't crash it), I noticed the aftermarket levers were binding and filed off an excess to allow the levers to return fully to their original position.

Another member of ridersite has noticed this as well. You didn't get the levers off the bay did you? We did...

The levers are Pazzo shorties. You actually use the plunger bit from the original levers which is what we had to file down. The levers are great and I would trade them for anything else. If I new a little bit more about this sort of problem then I could have avoided it.

To me the problem would seem to be with Pazzo. If their lever requires part of the master cyl to be altered, then the design of their lever should be altered. I bet it's not out by much, but you should be able to swap between Pazzo and OE parts without issue.

Steve.

[Kiwi_uk]

Chilli said:

Hello mate,

Sooooo glad you've got to the bottom of it. Wouldn't the bike want to sit up braking though, and have the opposite effect? Well, obviously not, but would be interested if someone could explain the physics!

How's "The Drive" treating you?

ps - Anyone fancy that trip to Spain. Corking track, fantastic weather, and I'll chuck in a bit of on-track tuition if you like???!!!!

Hey Man, Good to hear from you. I miss the sweet sound of a GSXR 750 starting up in the morning as my alarm. At least now I won't sleep in when you decide not to take the bike to work

Not in this case as the drag is all the time and gradually gets worse as things heat up and you sub-consciously compensate for it by using a little more counter steering and throttle.

BTW - Ian (my on track mentor) from work is going to join us in Spain for the Friday and Saturday. BRING IT ON!!

Edited by Kiwi_uk on Wednesday 10th October 11:46

[y2blade]

Busamav said:

Kiwi_uk said:

Turns out the after market levers I use were pushing on the piston in the MC enough for the pads to sit against the discs. When they heat up they expand causing the front wheel to lock when transitioning from brakes to power (not the normal place to low side).!

Thats the 4th instance i have heard of that involving aftermarket levers .

2 cases involved Busas going down in a straight line whilst at RAF Woodbridge doing top speed flyers, the last instance was last week on the A4 , a guy on an R1 felt his front wheel nip up just in time

ive heard that too from a few people in the trade...hence ive left the std levers on my blade

i was going to get those nice fully adjustable ones CRG roll-a-click ones like this

http://www.demon-tweeks.co.uk/products/ProductDeta...

Edited by y2blade on Wednesday 10th October 12:20

[Chilli]

Kiwi_uk said:

Chilli said:

Hello mate,

Sooooo glad you've got to the bottom of it. Wouldn't the bike want to sit up braking though, and have the opposite effect? Well, obviously not, but would be interested if someone could explain the physics!

How's "The Drive" treating you?

ps - Anyone fancy that trip to Spain. Corking track, fantastic weather, and I'll chuck in a bit of on-track tuition if you like???!!!!

Hey Man, Good to hear from you. I miss the sweet sound of a GSXR 750 starting up in the morning as my alarm. At least now I won't sleep in when you decide not to take the bike to work

Not in this case as the drag is all the time and gradually gets worse as things heat up and you sub-consciously compensate for it by using a little more counter steering and throttle.

BTW - Ian (my on track mentor) from work is going to join us in Spain for the Friday and Saturday. BRING IT ON!!

Edited by Kiwi_uk on Wednesday 10th October 11:46

Nice one! I can't wait now mate. Did you get me mail? I'll drop some cash round at the weekend.

Cheers.