Front brake failure

stevem · Jan 3, 2023

That is some photos of how everything was sitting when I took the front wheel out. I will try and convert the video from the day later tonight.The nut on the bracket is still torqued and it is the main line with the damage not the cross over. Maybe the main line wasn’t right and it got caught in the wheel and pulled the cross over out of the bracket and at the same time fully compressed the suspension cause the travel indicator is all the way to the bottom

stevem · Jan 3, 2023

Desmolvr said:
What front tire are you using? I had an issue after a couple of sessions using the new 125\70 as it started rubbing on the lines under the fender on 2018 V4S. At least that is when I started noticing the issue and immediately switched to the old front.

I am using the old 120, A mat had a similar thing as you with it rubbing on the sensor line under the guard.

Steven31371 · Jan 3, 2023

Alkhater said:
The brake lines are a pain in the ass to get routed through the little tabs in the front fender, especially on the carbon fender.

I'm guessing the line wasn't seated correctly through the tabs.

That’s be my guess too, or in the rear of the mudguard there is a screw in main clamp and the lines might not have been clamped in there properly.

Steven31371 · Jan 3, 2023

Lines aren’t seated right, need to be in that circled area, you can’t really pull them out of they are seated in that bracket right and the bracket is screwed in.

stevem · Jan 3, 2023

Steven31371 said:
Lines aren’t seated right, need to be in that circled area, you can’t really pull them out of they are seated in that bracket right and the bracket is screwed in.

View attachment 46606

That is right , my photo is showing after and the bracket is there still and the nut is torqued up but the line is out. The cross over line has a grommet on it that seats in that bracket.

SuperDomestique · Jan 3, 2023

When you reinstalled the lines into that bracket, was the cross over line in front or behind the line to ABS?

Alkhater · Jan 4, 2023

Do the split front “racing” brake lines mean that you lose ABS or can ABS be retained?

Steven31371 · Jan 4, 2023

craig bush said:
Brad Miller MotionSBK is another source for race lines. He’ll make them with dry break fittings if you want.

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Geezus Craig that bike and those forks look good

craig bush · Jan 4, 2023

Steven31371 said:
Geezus Craig that bike and those forks look good

Thanks bro!

RickD996 · Jan 4, 2023

Alkhater said:
Do the split front “racing” brake lines mean that you lose ABS or can ABS be retained?

ABS can be retained. You just need to run a new line from the pump to the calipers.

Steven31371 · Jan 4, 2023

bp_SFV4 said:
I don't see how its possible for the line to come out if the bracket is still tight to the fender.

He’s got new carts in his front forks, and presumably those are sprung right with the right amount of oil in there, and yet he still bottomed out the shock, which would take a fairly violent front loading event to do so, whatever that was may have been violent enough to somehow dislodge the lines from that bracket.

RickD996 · Jan 4, 2023

Steven31371 said:
He’s got new carts in his front forks, and presumably those are sprung right with the right amount of oil in there, and yet he still bottomed out the shock, which would take a fairly violent front loading event to do so, whatever that was may have been violent enough to somehow dislodge the lines from that bracket.

There's an oxymoron in there Steven!
If the forks have the correct springs and air gap, they won't bottom out.

xx

Steven31371 · Jan 5, 2023

RickD996 said:
There's an oxymoron in there Steven!
If the forks have the correct springs and air gap, they won't bottom out.

xx

Agreed, so something is off, either the fork inserts he mentioned weren’t installed right or sprung right, or had proper oil levels and weight, or an extremely violent load was placed on the front end. But that could have been the result of the brakes failing and him going over something

stevem · Jan 5, 2023

Steven31371 said:
Agreed, so something is off, either the fork inserts he mentioned weren’t installed right or sprung right, or had proper oil levels and weight, or an extremely violent load was placed on the front end. But that could have been the result of the brakes failing and him going over something

I ended up going down at approx 50kph and the bike ended up about 6 inches off a tyre wall. I have a video of it but it is hard to see cause I held the gopro button to long when I started it and it ended up recording double speed . Untitled video - Create and share your videos with Clipchamp I was wondering whether the front hit the wall and compressed but really don't think it did. Has anyone ever heard of a broken fork spring or would that cause it to bottom out. The sag from fully extended to me on it with gear was 30mm. I would normally run closer to 25 but left it soft as I hadn't been on track for a while and had it a bit more forgiving.

RickD996 · Jan 5, 2023

stevem said:
I ended up going down at approx 50kph and the bike ended up about 6 inches off a tyre wall. I have a video of it but it is hard to see cause I held the gopro button to long when I started it and it ended up recording double speed . Untitled video - Create and share your videos with Clipchamp I was wondering whether the front hit the wall and compressed but really don't think it did. Has anyone ever heard of a broken fork spring or would that cause it to bottom out. The sag from fully extended to me on it with gear was 30mm. I would normally run closer to 25 but left it soft as I hadn't been on track for a while and had it a bit more forgiving.

I never measured sag, it has zero consequence to bottoming. Or, indeed, just about anything. All it does, is tell you how much your bike sits, whilst stationary. Which, is a speed, to avoid on track.
Measuring your suspension travel on track is more useful. The sooner you move away from sag, the quicker your life will improve.

Taz · Jan 5, 2023

craig bush said:
Brad Miller MotionSBK is another source for race lines. He’ll make them with dry break fittings if you want.

View attachment 46599 View attachment 46600 View attachment 46601

I have a few questions regarding the swingarm cover you’re using so I sent you a pm. Would really appreciate your feedback.

stevem · Jan 5, 2023

RickD996 said:
I never measured sag, it has zero consequence to bottoming. Or, indeed, just about anything. All it does, is tell you how much your bike sits, whilst stationary. Which, is a speed, to avoid on track.
Measuring your suspension travel on track is more useful. The sooner you move away from sag, the quicker your life will improve.

For sure , I found it was useful to get it in the window at least and then like you say look at what you are using on track . The only problem with that is how much of the travel is the bike tracking and how much is when it is under the brakes?

stevem · Jan 5, 2023

At the end of the day I didn't have the lines set up properly so lesson learnt from that . The main thing now is why the ring on the forks is all the way to the bottom, I did hit a decent bump on the grass but not sure that would have done it.

RickD996 · Jan 5, 2023

stevem said:
For sure , I found it was useful to get it in the window at least and then like you say look at what you are using on track . The only problem with that is how much of the travel is the bike tracking and how much is when it is under the brakes?

You've two options:
1. Marker on the fork. A narrow zip tie is often easiest. Remember to move it up the lower stantion before every ride.
2. Data logging.

Steven31371 · Jan 5, 2023

RickD996 said:
You've two options:
1. Marker on the fork. A narrow zip tie is often easiest. Remember to move it up the lower stantion before every ride.
2. Data logging.

He had a marker on the fork, it had bottomed out.

Stevem did you see any signs of oil leakage from the shock?

It may be that in the heat of the moment you had a harder hit on the front end than you realized, or the oil level isn’t right…or the cart and/or cart springs are somehow not set up right internally.

If the right amount of oil is in there it would be REALLY hard to bottom out that shock like that.

I’d pull those carts out and maybe have a second set of eyes on giving those front fork setups a good looking over.

Front brake failure

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