nemeseri

Long story short, I'm thinking about buying a Trek Checkpoint bike. The carbon version has rear IsoSpeed, but it can't be adjusted to be firmer than the factory default. I saw a few opinion on this forum where people complained about too much flexing, especially on pavement: Trek Checkpoint SL: Is there a way to reduce flex in the isospeed decoupler?

IsoSpeed has been around for a while now. Does anybody have issues with too much flexing or moving around too much on the saddle during hard efforts?

If there is too much flex, maybe it's better to go with the alloy version of the frame. I plan to use the bike both on gravel and pavement and I've never had issues with comfort or the compliance of a frame. (I guess this might has something to with my relatively low weight (<60kg / < 130lbs)).

radroad

Fake news. The thread you linked shows unanimity: no other rider had the same problem.

Data point: I rode a rear isospeed only bike. The alu version when it was still being produced. It was just...terrible. The leaf spring was creaking like crazy and yet very difficult to actuate over bumps. The carbon version is supposed to offer more "travel?" but I understand you are concerned about that.

Maybe try a Diverge along with the Trek. The Diverge and Roubaix offer superior designs IMO. The future shock offers more travel and it is just that, actual travel, rather than frame flex.

WhyFi

This was one of the things that concerned me before buying my Domane, but it's been an absolute non-issue for me. Yeah, if I *try* to pedal like some over-caffeinated goon, I can induce bounce, but it doesn't happen otherwise. Put another way, the choppiness of pedal stroke necessary for me to bounce on the IsoSpeed is just a hair short of the kind of ridiculous effort that would have me bouncing on carbon frame without IsoSpeed.

Also, if you're looking at a Checkpoint and you're going to be running ~40mm tires, they'll probably give you saddle bounce well before the Iso does (unless they're over-inflated) - it's certainly easier to bounce on my 35s than even my 30s.

RShantz

I've got two bikes with rear IsoSpeed. Over 20k miles on them combined. I'm 135lbs so close to your size and spend more time than most out of the saddle - I like to stand when climbing the steep stuff. I only top out at about 1,000 watts so this may be a difference between us.

In any event, I've never had issues with frame flex. Now I do have a bit of flex when out of the saddle on my 60mm Bontrager XXX's. I've just opened up the brakes a bit to deal with that issue.

WhyFi

The Crosspoint only offers rear IsoSpeed. FutureShock is front wheel shock absorption, not rear. For the rear, Spec has the turkey-neck seat posts.

radroad

What's the crosspoint? I thought we were talking about the checkpoint lol.

Anyway, here's the diverge with front futureshock and rear cg-r suspension seat post. $3700 with carbon frame, 38mm tires with room for wider. Ultegra spec.

https://www.specialized.com/us/en/me...=227302-154306

WhyFi

Whatever chief. It still only offers rear IsoSpeed shock absorption, something that you have no practical experience with, and you're comparing it with FutureShock, which is front suspension - apples to oranges.

TiHabanero

My neighbor is the same size as me, 230ish pounds, and he said that he really doesn't know it is there or if it is working. I'd say it probably is just fine for under 200 pounders.

radroad

So where is this crosspoint? It might be a cool bike lol.

Actually I've ridden the aluminum isospeed. Learn how to read.

nemeseri

I really appreciate your input on this, very insightful, especially your comments on the tires.
I plan to use it for gravel rides with 40+ tires and for wet commutes with 28mm tires and fenders. Also I would like to ride the bike to the trailheads... I like my bikes fast and responsive I fear that IsoSpeed would make it feel like a truck. Even on 28mm tires. I will most definitely try out one with isospeed.

I do not worry about frame flex. More like because of any bouncy effect of the rear IsoSpeed.

Thanks for the recommendation and your experience with the alloy version. I did consider the diverge, but it's $500-$1000 more than the trek and has an extremely high stack. I know this is ok for gravel, but I'd like to set up my bike with a low front-end. Unfortunately I have very-very short legs, so low stack is important to me.

Dean V

I have no issues with the front/rear isospeed on my Domane.
However I wouldn't choose a Checkpoint if you want something "fast and responsive". Not because of the isospeed but it simply isn't built to behave like a race bike.
The Domane would be a better option if you can manage with a 35mm tyre limit. Stack might be a bit higher too.
Could be worth looking at CX bikes as well.

tigat

6 years and 50k miles on two Domanes. First version the rear was set, which I understand is the halfway point on the new slider versions. I'm a one-handed rider, so I climb and sprint seated. At 160 lbs., I run the slider as far down (flexible) as it goes. So does a 225 lb. friend who puts out massive power. If you have any doubts, your LBS should be willing to let you take it out on a hard effort, but I'm pretty sure excessive flex won't be an issue at your weight.

WhyFi

Yeah, I saw that. I also saw that the carbon frame is the primary consideration and topic of discussion. Thank you for your brilliant insight, though.

I'd be more concerned with the geometry than the IsoSpeed. TBH, I notice IsoSpeed most when I'm not riding it. My dedicated gravel bike, with 38mm tires at 35-40psi, handles bumps and jolts with far less grace and comfort than my Domane running tires at 70-80psi. That first big bump is always a shock, literally and figuratively, when I get on the gravel bike after exclusively riding the Domane for a while.

noodle soup

I also notice the IsoSpeed when switching bikes. My primary road bike is a 2015 Domane 6.9 disc, and the road bike I use for commuting is an ADK CF frameset from 2007.

For the first few rides on the Domane, I was often stopping to see if I had a rear tire puncture. Now I only notice the soft ride when I use the commuter bike for a few days, and then switch bikes.

stevoo

Trek rear IsoSpeed experience.
Yes, Domane 600 series.
Just comfy bump absorption. Really takes the sharp edge off.
No downside so far. You don't know it is there except it just rides nice.
I think the OP is overthinking it.
Find a test ride and decide for yourself.
Good luck.

Campag4life

Never say never but will give you my counterpoint to owning a bike with IsoSpeed. I just have never felt the need for one. I never believe the rear of any road bike is too stiff or rough riding. Perhaps we live on different roads. If I live on rough roads, I simple want a bike with bigger tires. Rougher still? A racing hardtail mountain bike.

I am not a fan of any suspension on a road bike. In fact, I have bought 29ers..all hardtails and have changed out the front shock for a rigid fork. I run tires and air pressure suitable to the terrain.

If riding real knarly stuff, I want a dual suspension mountain bike...likely carbon with 650 wheelset.

But for road bikes...I know never say never...but I prefer a Emonda over a Domane. I want the rear of the bike rigid. Any rear suspension bounce due to high pedal load/cadence is off the table. Non issue.

Btw, I feel the same way about the Roubaix with future shock. To me, its an abomination and would never own one. I feel more strongly about not wanting the future shock compared to IsoSpeed.

My opinion of course.

WhyFi

Which is coming from a position of ignorance, unless I'm mistaken and you've logged some significant miles on an IsoSpeed frame. It's great "suspension" for people that don't like suspension (something that we have in common).

radroad

LOL, you can't even figure out the name of the bike but you are in charge of evaluating the quality of posts?

Dean V

I wouldn't call isospeed suspension.
It is just a way of getting more vertical flex in the frame.
Also I have never noticed any bounce or anything close to it due to the isospeed on my Domane.
It rides just like a normal frame, super stiff BB (huge down tube), but as has been said already it takes some of the harshness out of the ride.

radroad

True, it's a simple leaf spring. Same for the front. The implementation was actually awful on the alu version which discouraged me from ever trying it on carbon. A lot of owners seem to like it though which is all that matters.

The advantage of a suspension seat post or stem however is that you can remove and reinstall on just about any frame. Not so true with isospeed or futureshock.

Campag4life

I don't need it or want it. I don't want tires made out of chewing gum either. Don't give me your opinion unless you have logged big miles with tires made out of chewing gum.

Let's see what else I don't want on a road bike... I don't want a rear view mirror on my road bike. I don't want fuzzy dice or curb feelers either...lol. Also, no integrated bar and stems or white wall tires or dual exhaust. When was the last time I ever felt the rear of my road bike was too harsh? Never. Let's see. What else don't I need on my road bike? Don't need a barbeque grill on one either. I can wait to get to a restaurant.

Dean V

Did you need Di2 either?
But now that you have it??

radroad

What do you weigh? Heavy (200+ lbs) or very heavy (250+ lbs) riders require a stiffer frame. That's fine. But lighter riders or riders with joint injuries or riders on very rough roads generally want a more compliant frame. An owner of a local shop gave a talk recently and said she recommended a minimum of 28mm tires for anyone riding on local roads since they were in such bad shape.

WhyFi

Ah, the #41ier experience. Can't beat it.

Speaking of experience, in a thread looking for those with actual experience to share, it seems to be unanimously positive at this point. That should be good enough for the OP. On that note, I'll bow out now - there's not much more to add and doing so would only encourage more flapping of the lips from the have-nots.

Best of luck, OP.

Campag4life

Di2 is an experiment. I may learn to love it more...or not. I am a late adopter and wanted to give it a try. I may sell the groupset and put mechanical Record on my new R3.
But I want to give the Di2 a good long test for a few months. It really does shift remarkably well. Nothing fits my hands as well as Campy shifters.