Using rear caliper brake as front. What length recessed nut?

[HovR]

So I'm looking at upgrading the brakes on my Dawes to dual pivot ones, but of course they have recessed fittings (my Dawes is a steel frame designed for non-recessed brake fittings).

One way of getting around this that I've heard is to use the front caliper brake on the back, using a regular nut and washers to fasten it on, and then use the rear caliper on the front (which has been drilled out to 8mm) with a long recessed nut.

Does anyone have any experience with this? How long will the new recessed nut for the rear brake on the front have to be? I've found 10mm and 18mm versions at Wiggle, and a 30mm version at SJS, but I want to ensure I'm buying the right thing.

Thanks in advance.

 

[RecordAceFromNew]

I use Sheldon's option 3 which does not need drilling the forks. Although John Allen questions its ability to counter torque I have never had any issue with my 531 forks.

The other option to avoid drilling the forks is to use special long bolts specifically designed for the purpose. Both Spa and sjs sell them. It also avoids swapping front and rear calipers (while retaining pads) which are sometimes marginally different.

But to answer your question in terms of what length sunken nut is needed why don't you just guesstimate from the depth of your fork crown and length of the bolt? CRC have cheap 18mm ones.

 

[HovR]

I use Sheldon's option 3 which does not need drilling the forks. Although John Allen questions its ability to counter torque I have never had any issue with my 531 forks.

The other option to avoid drilling the forks is to use special long bolts specifically designed for the purpose. Both Spa and sjs sell them. It also avoids swapping front and rear calipers (while retaining pads) which are sometimes marginally different.

But to answer your question in terms of what length sunken nut is needed why don't you just guesstimate from the depth of your fork crown and length of the bolt? CRC have cheap 18mm ones.

Thanks for the reply. I don't really mind drilling out the fork, despite the initial faff it will make it easy to take off the brakes for cleaning and maintenance.

I measured (possibly with questionable accuracy) the distance between the inside forward face of the fork crown to the outside rear face at around 25mm. This makes me think that the Wiggle 18mm nut may not be long enough?

SJS sell a 22mm length and a 30mm length (which could be used with the original sidepull washers to take up the extra length). Think I might order the calipers so I can see how long the rear brake bolt is before making a decision.

 

[RecordAceFromNew]

Think I might order the calipers so I can see how long the rear brake bolt is before making a decision.

Sounds like a good plan! For using the caliper with the longer bolt (probably ~25mm) up front 18mm is probably adequate - the bolt's thread usually does not extent all the way - you could run out of thread with a 25mm nut with your measurement e.g.