Brake block toe-in

My DuraAce BR-7800 came with adjustable pads. BR-6600 Ultegra comes with
the same setup. Maybe a different pad I do not know.

Quoted message said:

I have a Giant OCR2 road bike and decided to replace the rear brake
blocks on the Tektro dual pivot brakes.

The old blocks were Tektro P453 (one piece rubber) which came with the
bike. My local bike shop sold me Shimano Br-1055 R50T which looked
similar in the packet. I cleaned the rims etc and fitted and adjusted
the brakes, but I noticed the right hand toe-in was back to front with
the rear of the block touching the rim when the front of the block was
still 2mm or so off the rim. I could see no way of adjusting this. The
front of the left hand block just touches the rim first so appears to
be toed-in to some extent.

The brakes operate ok but I notice the rear brakes are more spongy, it
seems the rear of the right hand block makes contact with the rim then
the calliper moves slightly until the complete block contacts the rim.

Any suggestions how to cure this?

I was thinking of measuring the gap between the callipers to see if it
is parallel. Or fitting the blocks on the front to see if the reverse
toe-in is related to the block rather than the calliper.

The Tektro web site says the Tektro P453 are adjustable angle pads
which are presumably adjusted by the moveable threaded fixing in the
block and the dished washer holding the pad to the calliper. Am I
right in thinking these adjust toe-in?

The Shimano Br-1055 blocks didn't have dished washers or, I think,
moveable tread in the block. Was I sold the right blocks? I'm also
wondering if fitting the dished washer on the Shimano blocks would
sort my problem.

For some reason the right hand rear calliper has a bit of black tape
on it from new which I've never seen the need to take off.

I have no intention of trying to bend the calliper to resolve the
problem.

As I've spend the last 30mins of daylight cleaning my bike rather than
fiddling with the bakes I hope somebody here can help resolve this
problem.

Thanks.

Quoted message said:

I have a Giant OCR2 road bike and decided to replace the rear brake
blocks on the Tektro dual pivot brakes.

The old blocks were Tektro P453 (one piece rubber) which came with the
bike. My local bike shop sold me Shimano Br-1055 R50T which looked
similar in the packet. I cleaned the rims etc and fitted and adjusted
the brakes, but I noticed the right hand toe-in was back to front with
the rear of the block touching the rim when the front of the block was
still 2mm or so off the rim. I could see no way of adjusting this. The
front of the left hand block just touches the rim first so appears to
be toed-in to some extent.

The brakes operate ok but I notice the rear brakes are more spongy, it
seems the rear of the right hand block makes contact with the rim then
the calliper moves slightly until the complete block contacts the rim.

Any suggestions how to cure this?

Pull the brake cable or lever while tightening down the mounting bolt
(probably a 3 or 4mm hex) to "flatten" the pads against the rim.

Quoted message said:

For some reason the right hand rear calliper has a bit of black tape
on it from new which I've never seen the need to take off.

It is there for transport purposes. The spring action pulls the calipers
all the way open, causing the pinch bolt/washer to sometimes gouge into the
aluminum of the caliper arms during shipping. When mounted with cable
tension, this shouldn't occur and it can be removed or left alone.

--
Phil

[email hidden said:

"]... I notice the rear brakes are more spongy,...

The brake cable for the rear brake is considerably longer than the cable for the front brake. Cables stretch a bit under load (particularly when new), so with more cable to stretch the rear brake will always feel different than the front brake. Poor routing (that allows for excessive housing compression) and other set-up/assembly issues can make things worse. For V-s and Cantis frame/fork flex can also influence brake response. Sheldon Brown offers good advice.

Thanks Jim, Phil and Dabac for replies.

I'd previously tried tightening the pad bolt with the brake lever
pulled with no sucess. Good to know what black tape was for.

After more investigation in daylight and a phone call to my bike shop
it turns out they sold me non-adjustable pads when the ones I took in
for them to match were adjustable.

The spongyness seems to be the caliper flexing as the full face of the
pad makes contact with the rim. I'm confident its not the longer cable
or poor positioning. I'll be able to check this out when I pick up
adjustable pads. The web site you suggest looks good.

Thanks for your help.

Ian

On Jan 29, 9:35 am, [email hidden] wrote:
---snip---

Quoted message said:

The spongyness seems to be the caliper flexing as the full face of the
pad makes contact with the rim. I'm confident its not the longer cable
or poor positioning. I'll be able to check this out when I pick up
adjustable pads. The web site you suggest looks good.

---/snip---

I've run into this same problem - even with adjustable pads. It turns
out that the tolerances in the calipers were just not precise enough.
A little fiddling with a carefully adjusted crescent wrench provided
just the right amount of toe-in, and substantially firmed up the feel
at the lever.

HTH,

SYJ