Trainer only frame design

[JD Reich]

Good Morning,

Hope you are all doing well!

I am working with a customer who would like a frame built that will only be used for training/racing on his smart trainer via Zwift. The trainer is of the variety where the rear wheel is removed and the dropouts mount to the trainer via quick release.

Aside from factoring in his weight and that he is a strong rider/racer, do you have any suggestions as to if the tubing choice, CS length, etc...should be any different than what I would use if this was going to be ridden on the road?

I was beginning to wonder if due to how stationary the rear of the bike is while attached to the trainer, even during sprint, if shorter and more substantial CS and ST might be appropriate.

Thanks!
JD

[e-RICHIE]

I would make the frame as you normally would, and when it's atop a trainer it's a trainer bicycle.

Serious.

[JD Reich]

Thank you Richard, I appreciate that. Will do.

I assumed I was probably over thinking.

Have a great afternoon!

[DBordewisch]

Just some thoughts. Threaded 68mm. bb, Easy to fix, always replacements available, a drain hole, no brake cable stops, No internal derailleur cables, set collar so it can be replaced, 27.2mm. seatpost dia., press in headset cups, can the frame be internal coated or plated with something to prevent rust/corrosion? Short chain stays may equal poor shifting, clamp on front derailleur. All things that might avoid problems from the sweat.

[false_aesthetic]

The only thing I would add to the above is looking into a 2-coat powder coating or maybe Cerakote.

I don't know the specifics of the 2-coat system but my local powdercoating shop suggested it for stuff that lives outside + near the ocean. Their standard corrosion resistant powder coatings break down with extended UV exposure.

[Andrew R Stewart]

The only aspect i will bring to this thread is that of few plans remain static forever. Needs shift, bikes come and go over the years, what might be viewed as a trainer stand bike in it's beginning could well be pulled into some other service 5 years later.

So my suggestion is to build a bike that you can ride outside. Andy

[Tristan]

I've never understood why these trainer bikes have a functional front wheel - it takes up space and has weird wheel-flop characteristics. I'd suggest a reasonably normal looking frame but with a special front-end.

You don't need / want a headset so instead could have the bars rigidly mounted to the frame. The 'fork' can be replaced with a nice height-adjustable floor support, maybe with a build in holder for his PC monitor or ipad?

I'd take cues from the Tacx bike
https://tacx.com/product/neo-bike-smart/

[JD Reich]

Thank you all so much for the thoughts and suggestions! Very very helpful

Completely agree that special consideration needs to be given to the paint/powder/cerakote both outside and inside of the frame since it is subjected to so much more salt. Same with the additional components as you mentioned that make room for rust/corrosion.

I do like the idea of building a bike, as I normally would in the event that he wants to pull it off of the trainer someday....he'll then be able to take it outside!

With that being said, Tristan, my mind was going down the same path as yours. This particular customer is on my Zwift team, and I'm quite certain this will be a longterm indoor bike only. I was getting quite creative in my mind to try to think of a neat design similar to the wahoo bike. You are right; you don't need a front wheel or traditional fork and like you said, it might function better without a front wheel. Zwift recently added a turning capability with an add on device that your front wheel sits in, which is something I need to consider.

This has been a fun project to chew on and design.

Thanks again!
JD

[bigbill]

I don't think I'm allowed to post here, but I spend a lot of time on a trainer in the winter, specifically a Wahoo KICKR. Pretty much all the trainers will take a thru axle these days. I use an older Ti frame with QR. IMO, for a dedicated trainer bike, a TA makes sense. Might as well add disc brake mounts in case it ends up outside.

[Andrew R Stewart]

I haven't spent hardly any time of a trainer which fixes the front wheel in place, or more to my point the handle bars won't rotate. That the bars can move with my pedaling just seems so right. It feels awkward enough to me to ride a stand that prevents the bike's swaying from side to side. So a trainer bike like structure without this natural movement would, to me, not be on my planning board. But I view indoor riding as a path to better out doors riding, not an end to it's self. Andy

[Tristan]

I'm confused: customer obviously spends significant time on zwift and wants a dedicated platform. Why wouldn't you build this?

If s/he just wants "a bike to use on zwift" there are a hundred slightly cracked Cannondale or Giant frames out there for free.

You've got a rare opportunity to build something special: don't waste it building a regular frame. Talk with the customer and learn what they want, then deliver it. Hell, you could be the world leader in zwift bikes after this.

Plenty of people and companies make car simulator rigs so don't think dedicated zwift bikes aren't a thing.

[EricKeller]

I have considered building a trainer-specific frame. I don't like having a front wheel on my trainer, but I think having the handlebars move to some extent is a nice touch. The other thing to consider about the front wheel is the kickr climb, which replaces the front wheel. If you think that's a gimmick, zwift is adding steering support, and I think that requires a front wheel as well. That's a gimmick, but it might make racing so it's not just a group time trial. Making a support that replaces the wheel and looks halfway decent is a significant design task which may not be worth it in the end. Unless you have a great idea on this subject and sell the customer on it, maybe stick to a front wheel. If I do this, I'll probably just not worry about tire clearance. And then I'll regret it later when I decide to put a wheel in the back.

[JD Reich]

I'm confused: customer obviously spends significant time on zwift and wants a dedicated platform. Why wouldn't you build this?

If s/he just wants "a bike to use on zwift" there are a hundred slightly cracked Cannondale or Giant frames out there for free.

You've got a rare opportunity to build something special: don't waste it building a regular frame. Talk with the customer and learn what they want, then deliver it. Hell, you could be the world leader in zwift bikes after this.

Plenty of people and companies make car simulator rigs so don't think dedicated zwift bikes aren't a thing.

You're exactly right on all points Tristan; maybe not the world leader but, hey have to start somewhere!

Thanks Andy, Eric and Bill for your thoughts as well. I ride about 250-300km on Zwift each week and race frequently as well, and do like to have movement in the front end. It just seems more natural. That being said, I haven't tried the kickr climb, for example, where I wouldn't have that side to side turning movement with the front wheel.

Again, this has been a fun endeavor to brainstorm on, and appreciate the ideas on how to get there. I've had some good conversations with the customer as well, who has some good ideas.

Have a great day everyone!

[PJN]

How about building a “zwift fork”?

Build the frame like you normally work with geometry for on road behavior but then build a Beefy, telescoping (For leveling) fork replacement to support the bike without the wheel taking up space. Goal would be stability for zwifting in low footprint space but still be swapable so the bike can be ridden outside.

Put a thrust bearing between the bottom support plate and the lower stanchion (for lack of a better word) so the bars can turn but not mar the floor. You could also make it lockable via a pin if the client didn’t want the bars to move.

I dunno what else...