How big are the tolerances on seat height? ISP questions

Discuss light weight issues concerning road bikes & parts.
Skorp
Shop Wrench
Posts: 91
Joined: Thu May 30, 2013 12:54 am

by Skorp

Hi!

I'm thinking of buying a used ISP frame.
The seat height is around 0.5cm lower than my current frame.. ( altough the previous owner doesnt sound like the most technical person.. i guess he might measure wrong)

How much do you really feel? Will my knees hurt and my power drop if its 1cm to low?
How much is it possible to adjust with a Addict R2 2008 frame?
Cheers,

by Weenie


brearley
Posts: 354
Joined: Mon Aug 11, 2008 10:08 pm
Location: Hull

by brearley

there are some options.
1, you can fit a 5mm spacer/offcut of old isp if the seller has some left over.
2, use a standard seatpost inside the isp, you'd need to cut and slot the isp then use a standard seat clamp after filing the isp to the correct size.
Basically you have room for movement, if it's way out cut the isp right down and use a standard post.

I am going down a different route of not using an ISP clamp.
I've cut down an old seatpost to around 7cm, filed a groove for the lower cradle which I've made using old fork steerer cutting. Once I have the lower cradle to the correct seat height with the new seatpost in I will drill through both the ISP and the seatpost then use a thru-pin like is used for most zero setback seatposts. This should weigh around 60g and if i ever need to change the saddle height I can either use a higher lower cradle or use another seatpost of the same method.

mattr
Posts: 3542
Joined: Fri May 25, 2007 6:43 pm
Location: The Grim North.

by mattr

Might be best off measuring to the saddle rail, rather than the top of the saddle. The lowest to highest saddle profiles varies by more than 2cm.
And i think the scott allows 20mm of adjustment. But you don't know where in the range of adjustment the topper currently is........

And 1cm out for saddle height would cripple me. Try dropping the saddle on your current bike and see how it feels.

Skorp
Shop Wrench
Posts: 91
Joined: Thu May 30, 2013 12:54 am

by Skorp

Do you need to use spacers when raising the saddle height?
The stuby's clamp is not enough?

If its possible to adjust 20mm then i guess i can find my correct fit. Maybe there is different lenght of stubbies?

hasbeen
Posts: 556
Joined: Tue Feb 07, 2012 7:17 pm

by hasbeen

First, 1mm can be felt by most cyclists if they ride a lot.
My Casati ISP is trimmed, seat clamp added, and a regular 31.6 post put in. This allows me more saddle options as I am currently "searching for the holy grail" on that one. Essentially it is an extended seattube when done this way. It also weighed the least of the combos I had for options. I have since picked up a Woodman topper but wont go that route till I settle on a saddle.
As a side note: I adjust my saddle position a lot more than most so the way i set it up is easier to make those little mm adjustments.
Casati Vola SLi and Dolan Preffisio
viewtopic.php?f=10&t=108931" onclick="window.open(this.href);return false;"
btompkins0112 wrote:
It has the H2 geo......one step racier than a hybrid bike

Skorp
Shop Wrench
Posts: 91
Joined: Thu May 30, 2013 12:54 am

by Skorp

Im really a novice when it comes to pedaling. (But a bike mechanic and a avid DH/AM/biketrials rider)
My current frame have some seatpost slipping, icant notice until my knees hurt from too low saddle height.. atleast almost :mrgreen: :)

eric
Posts: 2196
Joined: Tue Nov 11, 2003 9:47 pm
Location: Santa Cruz, California, USA
Contact:

by eric

This frame does not fit you. Don't buy it.

A lower seat height might be better for you. But there is an equal chance that you actually need a higher seat. And then there is the problem as noted above of different saddles having different 'stack height' from the rails to the seat. As a new road rider you will be changing position and saddles to find what works for you.

Unless you are going to do the seat post mod this bike's adjustments will limit your position or saddle options.

User avatar
legs 11
Posts: 3657
Joined: Tue Jan 23, 2007 11:22 am
Location: Leg hurty

by legs 11

If you're not too fussy with your saddle type you could gain around 10-15mm if you go for a higher saddle rail/top thickness.
The old Concor Light has a huge rail/top measurement.
You really need to keep the height correct if you can......I get ITB problems as soon as I ride even slightly too low.
Pedalling Law Student.

5 8 5
Posts: 1353
Joined: Sat Jul 29, 2006 2:36 am
Location: UK

by 5 8 5

I agree, don't buy a frame and try to make yourself fit it!

But, in this case you should be okay. The standard Stubby supplied with the frame has 15mm of adjustment.

There's also an extra long version which I think is 70mm (compared to the original 50mm) so an extra 20mm of seat height is available.

Skorp
Shop Wrench
Posts: 91
Joined: Thu May 30, 2013 12:54 am

by Skorp

Made the seller measure from centre of crank, to the rail.. 74cm, while my bike have 73cm :) I obviously have a tall saddle, and his saddle is lower.
So the fitment is perfect! :)
At 74cm the stubby was all the way down.

lannes
Posts: 418
Joined: Sat Nov 10, 2007 9:51 pm

by lannes

Skorp wrote:Made the seller measure from centre of crank, to the rail.. 74cm, while my bike have 73cm :) I obviously have a tall saddle, and his saddle is lower.
So the fitment is perfect! :)
At 74cm the stubby was all the way down.


shouldn't you measure from the bottom bracket to the "top" of the saddle, then add in the crank length and compare the measurements.
The height of the saddle above the rail will be different unless your planning to use the same model.

I guess with an ISP, if it is cut too short you can use spacers to raise it, the Giant ISP comes with a heap of multi-height spacers.
I think you can safely add 2-3cm of spacers to the ISP, provided there are none in the first place
Last edited by lannes on Sat Dec 14, 2013 1:23 am, edited 1 time in total.

Skorp
Shop Wrench
Posts: 91
Joined: Thu May 30, 2013 12:54 am

by Skorp

What is important for me is this measurement.
I am currently running a bigger saddle, because i broke my Selle Italia flite, and i have bought a smaller BBB Saddle..

rowdysluggins
Posts: 349
Joined: Tue Apr 27, 2010 2:36 am
Location: Taylosville, Utah

by rowdysluggins

I think the standard 50mm Ritchey seat topper has about 15mm of adjustability, and you can buy a 70mm version to give you 20mm more height.

mattr
Posts: 3542
Joined: Fri May 25, 2007 6:43 pm
Location: The Grim North.

by mattr

lannes wrote:shouldn't you measure from the bottom bracket to the "top" of the saddle, then add in the crank length and compare the measurements.
The height of the saddle above the rail will be different unless your planning to use the same model.

It's the easiest way to measure frames with isp. As it's very rare to use someone else's saddle...... Most riders tend to stick with the same model of saddle for a long time. I've been running the same for ~10 years.

mattr
Posts: 3542
Joined: Fri May 25, 2007 6:43 pm
Location: The Grim North.

by mattr

OP, sounds like this frame is nearly the right size for you, and has some adjustment still available to use.

by Weenie


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