Triumph Sprint ST 955i - front caliper sticking?

[MrGTI6]

Hi,

I believe the front caliper is sticking on my bike but as a complete novice I though I'd see what others think first!

The bike is currently residing in my parent's garden! It's nigh on impossible to push, and the brake light is permanently on when the ignition is on. The second I stop pushing it, it stops dead. Paddling the bike, I can move it about an inch at a time and it's exhausting.

Every now and then it frees up a bit and moves freely, and when it does the brake light goes out. Even then you can hear the front brake slightly.

Just wanted to see if others would agree that this sounds like a sticking front caliper? Or perhaps something else?

The bike is a 1999 Triumph Sprint ST 955i.

Thanks.

[Biker9090]

Have you checked both the lever and pedal for movement? The light will be triggering from one of them. If it was just a caliper then the light wouldn't be on.

[MrGTI6]

Biker9090 said:

Have you checked both the lever and pedal for movement? The light will be triggering from one of them. If it was just a caliper then the light wouldn't be on.

Thanks, I mentioned the brake light because this was the bit that made me doubt it was the caliper sticking.

Sorry to ask a stupid question, but how would I go about checking the pedal/lever for movement? They both feel "normal" to me, but given that it's my first bike, I don't really have a lot to compare it to!

[Tango13]

MrGTI6 said:

Thanks, I mentioned the brake light because this was the bit that made me doubt it was the caliper sticking.

Sorry to ask a stupid question, but how would I go about checking the pedal/lever for movement? They both feel "normal" to me, but given that it's my first bike, I don't really have a lot to compare it to!

Is there a gap between the front brake lever and the master cylinder piston and does the lever move freely?

[KTMsm]

Assuming you've checked it is the front brake - the fact the light says on suggests its the master cylinder sticking

I'm sure a quick google will show you how to check / clean / rebuild one

If you want to check - crack the bleed nipple when they're sticking - fluid will come out but if the brakes are then free - it's the master. If they're not it's the caliper

[ssray]

Where are you? Maybe someone local could pop round and advise?

Calipers are fairly simple, most problems are dirt/corrosion related

If the pistons are dirty then they may stick and not fully return

The seals get corrosion behind them and make the pistons stick.

As long as you know one end of a spanner from the other YouTube is your friend.

Best thing I've bought for brakes recently is a £12 vacuum brake bleeder from eBay

[MrGTI6]

Thanks for the responses. Had a manic evening so haven't had a chance to properly look at it yet, but all the replies are much appreciated.

It's too dark out to do much with it now, but I did just try pushing it round the garden expecting it to be impossible. For no apparent reason, it's now moving freely and the brake light is off.

So I pulled the front brake lever and when it returned to position the brake light stayed on. The bike remained easy enough to push around. Pushing the lever back (away from the handlebars) caused the brake light to come off, but when released back to its natural position, the light came on. Repeated this, and after four or five times, the brake light remained off.

Tried again and the same happened. It's as though the lever isn't quite going all the way back. But at no point this evening has it been sticking badly like it was earlier.

When it has been sticking badly, pushing the lever away has made no difference.

I hope this makes sense!

I'm going to follow some of the advice tomorrow, but thought I would share the above in case it narrows it down!

[v9]

I’ve a 955i Speed Triple, which has, I think, the same braking system. I had a similar issue with the lever not fully returning and the light staying on. I stripped the brake system and rebuilt the lot with new seals and spring in the master. It’s pretty straightforward (and strangely satisfying thing) to do, but you do need the correct tool to get the pistons out of the calipers. If you’re anywhere local (see your profile says Kent) I’d be happy to lend the tool and help take a look. I’m on the Kent/Sussex border near the coast.

MrGTI6 said:

Thanks for the responses. Had a manic evening so haven't had a chance to properly look at it yet, but all the replies are much appreciated.

It's too dark out to do much with it now, but I did just try pushing it round the garden expecting it to be impossible. For no apparent reason, it's now moving freely and the brake light is off.

So I pulled the front brake lever and when it returned to position the brake light stayed on. The bike remained easy enough to push around. Pushing the lever back (away from the handlebars) caused the brake light to come off, but when released back to its natural position, the light came on. Repeated this, and after four or five times, the brake light remained off.

Tried again and the same happened. It's as though the lever isn't quite going all the way back. But at no point this evening has it been sticking badly like it was earlier.

When it has been sticking badly, pushing the lever away has made no difference.

I hope this makes sense!

I'm going to follow some of the advice tomorrow, but thought I would share the above in case it narrows it down!

[KTMsm]

I'm unsure how the front brake light works on that model, most are a simple push switch activated by the lever

You could of course have two problems, a sticky switch and a sticky caliper both are common

[Jazoli]

It's a simple push switch on the Sprints.