Brooks saddles and Giant defy.

[wyre forest blues]

I have a Giant Defy Advanced pro 1 (2017) with a D shape seat post. At the saddle attachment point it indicates that the saddle rails must be 9mm. diameter. My B17 Brooks saddle rails are 6 (or 7?) mm. Consequently the saddle rails moves on the locking attachment. Has anyone any suggestion how to overcome this problem. I have considered aralditing a thin piece of metal to the seat post attachment to decrease the required diameter of the rails but it seems like a bit of a botch job to do that.
Thanks in advance.

 

[Cycleops]

New seat post or clamp?

 

[Kempstonian]

A few winds of insulating tape round the rails to thicken them up?

 

[stalagmike]

Bit of old inner tube or Alu drinks can as shim?

 

[Vantage]

Given the forces going on in that area and the small clamping area, something that will compress like insulating tape or inner tube wouldn't be my first choice of materials.
You might be able to layer up a roll of aluminium drinks can or even better, a bit of copper tubing from B&Q or somewhere.
Or, just get a better fitting seatpost.

 

[Cycleops]

I think that's the only answer @Vantage Should only set the OP back about thirty quid.

 

[rogerzilla]

You'll probably want one with a lot of layback too, as Brooks rails are shorter than normal and seat angles of modern Taiwanese frames are steepish.

 

[biggs682]

I think you might struggle to change the seat post due to the shape ie "D"

 

[Globalti]

Treat the bike to a modern saddle?

https://goo.gl/images/EC9noX

 

[Cycleops]

I think you might struggle to change the seat post due to the shape ie "D"

Although the frame seat tube is D shaped there is an insert which allows the use of a standard round seat post. I'm sure the OP can confirm or deny this is the case on his model.

 

[biggs682]

Although the frame seat tube is D shaped there is an insert which allows the use of a standard round seat post. I'm sure the OP can confirm or deny this is the case on his model.

That would make sense

 

[wyre forest blues]

Thanks for all your replies and suggestions. I asked Brooks for a solution but unfortunately there is no shim etc to enlarge the rail. The only saddle they sell with a 9mm rail is one of the cambrian models. I dont think that wrapping insulating tape or a length of inner tube will be substantial enough to prevent movement. It will require some sort of metal or similar product that has no 'give'. Perhaps a shim of aluminium can or copper tube might do the job as suggested. It doesnt necessarily need to be wrapped around the rails... it might be possible to araldite it to the seat post clamp to effectively reduce the size of the gap. I'm not sure if there is an alternative seat post, either D shape or round with a conversion. I would have thought unlikely. I think that solution might be expensive... the post is carbon and I want to maintain the quality. In reply to changing the saddle..thanks for the suggestion but have tried several in the past and for me Brooks B17 is best for me.
I'm sure I will come up with a solution, and will reply on this thread in due course.

 

[Ian H]

I'd make up 2 or more shims roughly as this drawing. 2 sides linked for ease of assembly. Place under and over the rails. Drinks can aluminium should work fine.

 

[wyre forest blues]

Thanks Ian... That would fit perfectly . With the saddle rails in place there is a noticeable gap between the bottom of the rail and the top of the base clamp.

 

[DRM]

Although the frame seat tube is D shaped there is an insert which allows the use of a standard round seat post. I'm sure the OP can confirm or deny this is the case on his model.

In the case of a Giant Defy, I would be very wary of using any type of adapter to fit a round seat post, the rear of the D shape is quite flat, while the front is quite pointed, so there would be no support from the seat post that is left inside the frame, a round post would only touch at the clamp, I feel certain that the instruction manual specifically states not to have the seat post past the minimum insertion mark, plus I’m sure there have been cases of the frame cracking near the seat stays due to having the seat post too far out & flexing the frame when it’s ridden.