ISP saddle height adjustment

Discuss light weight issues concerning road bikes & parts.
rgamble
Posts: 63
Joined: Wed Feb 01, 2012 12:34 am

by rgamble

The following pertains to a Scuro Rs but probably is relevant to any ISP frame:

I plan on switching from a Flite saddle to an SLR. They are ~12mm different in height.

To account for the difference I plan on cutting a 12mm piece from the seat tube waste stock and simply placing it on top of the seat tube, acting in effect as a shim or spacer, then fitting the seat tube cap over top and be done with it.

Alternately I could simply move the cap up 12mm and clamp it in place, an approach that could result in slippage.

Anyone see any problem with the first solution? If that's the case, please let me know.

Thanks.

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bobbyOCR
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by bobbyOCR

There are a few frames under that name so I'm not sure which one you're referring to.

I'm going to assume it's the Deda, in which case they use a circular clamp IIRC? The minimum insertion is generally 50mm. In terms of using the offcut, go for it. The only issue I can think of is if the offcut being clamped as opposed to the seat mast, but this is unlikely since the lower portion is the only part doing any clamping on most mast heads anyway.

You can always buy a longer cap, like the KCNC Majestic. This will give you more adjustment in the future.
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by Weenie


Mr.Gib
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by Mr.Gib

There must be spacers under the top cap (and previously removed portions of the ISP can work as spacers). Either that or the cap sits directly on the ISP. No way you can clamp with a gap and expect it to hold. Any force adequate to stop the cap and seat from slipping down would surely crush the ISP.

FWIW my Giant came with a vast selection of alloy spacers.
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roca rule
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by roca rule

i second that
my look 595 and my ridley helium had plenty of spacers.

rgamble
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by rgamble

Thanks all for the info. The apropriate solution was so obvious I found myself second guessing it.

To BobbyOCR's point: yes, it's a Deda with the teardrop shaped ISP. The single 4mm fixing bolt on the cap is 3 cm beneath the top of the cap as illustrated in the attachment.
Attachments
isp.jpg
isp.jpg (8.46 KiB) Viewed 3787 times

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elviento
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by elviento

Some ISPs are designed to require spacers and some aren't. As long as they are properly designed and manufactured, I'd suggest using it as it's designed.

BTW, generally expander type ISPs require spacers while external clamp types do not.

That said, if you do see slippage, adding a spacer definitely won't hurt you.

Take it from someone who spent way too much time pondering over ISP design.
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thisisatest
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by thisisatest

Agree with above.
Wilier cento1 uses a thick aluminum slug that fits into the top of the seat tube. That's probably needed for sufficient clamping force when the head is not mounted flush. It would at least be convenient to be able to do that until you're sure where you want the saddle. Otherwise, you could spend a week cutting ever-so-slightly thinner spacers.

Valbrona
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by Valbrona

Use it with a gap and I think you will get slippage. Use DIY spacers and I would recommend that you monitor for any problems, switching back to a Flite if any arise.

thisisatest
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by thisisatest

Why would the isp act any differently than any other seatpost, or Trek's no-cut seat mast?

rgamble
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by rgamble

As a point of information, a quick confirmation measurement of the 2012 SLR saddle before cutting the shim revealed only a 5mm height difference between it and the Flite. I had used a first generation SLR for the original measurement yielding 10mm.

I'd attribute the difference to the additional 2mm vertically the 7x9 rails provide combined with the additional padding the 2nd gen SLR has compared to the original which is hard as a rock.

Also, I set the cap clamp bolt somewhere between finger tight and 2nm.

Valbrona
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by Valbrona

You would think saddle manufacturers would all be clever enough to supply online drawings of their saddles so as to make buying one in these ISP scenarios a little bit easier. No such luck.

rgamble
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by rgamble

Good point. While saddle makers do provide length and width information it's as if handlebar manufacturers only provided 2 of the 3 important dimensions.

At first I thought it was a result of the relatively recent appearance of ISP however the same consideration comes into play regardless of the seatpost type.

This could be viewed as an ISP shortcoming but in practice it’s about the same as changing stem height with threadless stems.

Subjective aesthetics aside on balance I'd have to give it to ISP as there're no clamping forces, slippage, or yaw to contend with.

Geoff
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by Geoff

This is one of those situations where the FitStik has paid for itself over and over. Just throw-it-on the bike, adjust, take a reading, then add or subtract from your known position. You then know within 1mm how much spacer to add or how much ISP to remove in seconds. Takes all the guesswork out of it.

xcnick
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by xcnick

I'm in the same boat as the OP

I also have a Scuro RS, To adjust I would use the offcuts from the seatpost if you have them and make shims.

I use a spesh Toupe and sick to death of the sagging issues. I really like the shape and cutout when the saddles are new. Fortunately the stack of the Toupe is very low and any saddle I pick will require cutting of the mast. I need to find a new suitable saddle before my fit in months time ideally!!

by Weenie


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by 5 8 5

Valbrona wrote:You would think saddle manufacturers would all be clever enough to supply online drawings of their saddles so as to make buying one in these ISP scenarios a little bit easier. No such luck.

Selle Italia do. Under "Utility" on the product page there's "technical drawing".


I agree with xcnick. Use the offcuts. You could form a spacer from a piece of rubber. I use nylon washers but it's easier for me as my ISP is round.
Also use carbon paste. It'll mean you don't have to torque the clamp as much.
Attachments
SLR Ti.jpg

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