Designing a custom titanium frame - gravel mountain adventure bike

[em_reeze]

I have been working on designing a custom frame I want to have Waltly build out of titanium. I have been drawing some bikes I like in bikeCAD to get the basic dimensions. The dimensions I am looking at come out very similar to what TripleDot just built to emulate the Niner SIR9 but with a little bit slacker hta and a few other differences.

I thought I wanted to make a drop bar gravel bike but I think I would rather have a mountain bike (with flat or alt w style bars) that I can ride on road, gravel, some smooth trails, and also take it on some longer adventures. I will use mountain bike brakes and a one by drivetrain. It will start out with a carbon rigid fork but I want to be able to put on a 100 mm suspension fork on the front if I want in the future.

Basic dimensions (I am not 100% set on these yet):
hta = 67.5
sta = 74
seat tube length = 485 mm
top tube = 625 mm
head tube = 135 mm
chainstay = 427 mm
wheelbase = 1142 mm
BB drop = -60 mm
reach = 440 mm
stack = 623 mm (I like bikes that are more upright)
fork axle to crown = 483 mm (rake 51 mm)

Components and wish list for the 29er:
1. max tire size = 2.25" (61 mm) but 2.3" would be nice if possible.
2. front chainring = 40t
3. rear cassette = shimano xt 10-51, 12 speed
4. bb height around 300mm with 47 mm tires
5. I was thinking of buying a salsa firestarter 110 boost fork
6. boost rear wheel (148 mm)
7. curved seat tube (like niner SIR)
8. rider weight with gear to support 100 kg
9. I am 6' 0" and weight 85 kg (85cm inseam)
10. Threaded BB (either T47 or BSA)
11. I like the water drain hole under BB so I will ask for that feature too
12. 44/56 mm head tube for tapered fork
13. Internal routing for dropper post (at least in the seat tube with external routing up the down tube possibly)
14. handlebars will be either Salsa bend 2 (23 deg) 710 or 740 mm wide or the Carver MyTi bars at 710 mm
15. I might do external cable routing for the hydraulic disc brake cable.
16. I am not sure if I should do external or internal cable routing for the rear derailleur cable. Any thoughts? I have recabled my internal rear derailleur cable a few times with my mtn bike and it is okay.
17. Seat post dropper at 31.6 mm seems like the most common so I will shoot for that.
18. Oval chainstay tubes

Questions I have you guys might be able to help answer:
1. How much of the geometry and exact information (components I plan to put on the bike) do I need to start talking with Waltly?
2. I think the chainline will be 52mm but how do I determine this or will it be shown on the CAD drawing?
3. Any suggestions on what crank to use? I was thinking the new XT 8120. Is a lower Q factor better? It might not be possible to get a low Q factor with wide tires. I know this is all a balancing act.
4. Can I put a 40T chainring on this crank or another crankset that will fit the build?
5. Can they run internal cable routing continuously if I use a T47 BB?
6. What are the pros/cons of BSA vs T47 BB? 73 vs 68 mm?
7. What derailleur hanger does Waltly Ti bikes come with or is this something I need to determine?
8. I would like to include three bottle cages but I am curious if it is worth having Waltly put bottle cage mounts on the top side of the top tube for a bolt on bag or are the velcro bags fine?
9. Is it worth adding mounting points for a rear rack?

[tripleDot]

Alright! Alright! Alright!

1. Contact Waltly, they will help you fill out the necessary numbers. In my case, the most crucial info was the fork length & offset. You can also change the figures as you progress. They will ask for a 50% downpayment before they officially begin with the project planning. Plus the planning stage can take a few weeks.

2. You can just tell them the chainline value you want. While your CAD drawing would help, it is not required. I didn't have that, I just list down the numbers, accompanied by pictures of Niner SIR frame & it's geo-chart. Any numbers I didn't list that they required, they asked. If I don't know, they suggest but I decide. They will come up with the drawing for you to check & approve. And every time you have a revision, the drawings will be updated accordingly.

4. They will inform you if the 40T is doable with respect to your tire size & chainstay length.

3., 5. & 6. I'm afraid I'm not technical or knowledgeable enough to answer these questions.

7. I never asked them but I believe they have a default derailure hanger based on your chosen dropout. They might have options for you to choose. In my case, I was deadset with the sliding dropout with those brackets... so I didn't bother to ask.

8. Top tube mounts for bags aren't a bad idea. It gives you more options for choices of bags (I do see a lots of bolt-on bags on the market nowadays) and mounting strategies. The only hitch I see is bolt-on bags looks/works better on flat top tube. Perhaps you can ask Waltly if they could use oval top tube or offer a square-ish tube. After all, Litespeed Ultimate Gravel Ti Bike is sporting a square-ish top tube.

9. I believe it is worth it. The only reason I didn't have them on my 'Niner SIR' was because I already have a gravel bike with those features. I pretty much already defined their roles. And I believe these added features won't cost too much. It'll probably fit in the basic rate. In fact, I'd go ahead & ask if they can build the rack for that frame.


Suggestions:
1. You could consider your max tire to allow you to slap on a 27.5+ tires. I had consider the idea but having rode a 29+ and extremely loved it, I know I want a dedicate 29+. But just a thought.

2. You might want to tell them if you want polished or brushed or sand blasted (?) finish. While I didn't ask, I have a feeling you can have mixed-finish.

3. If you have pictures of features you like/want, show it to them. They will let you know if it's doable or not. Heck, we took a month of trying to make that 420 chainstay length on a 29+ frame work but we couldn't. What I mean is, they will try to give you what you want. You may not always get it but at least it wasn't without some effort.

[bxcc]

3. Any suggestions on what crank to use? I was thinking the new XT 8120. Is a lower Q factor better? It might not be possible to get a low Q factor with wide tires. I know this is all a balancing act.

5. Can they run internal cable routing continuously if I use a T47 BB?

6. What are the pros/cons of BSA vs T47 BB? 73 vs 68 mm?

tripleDot explained most of your questions the same as I would so I won't repeat it.

3. Any crank will work as long as it has an appropriate chainline for boost rings and will fit a 40 tooth ring. Even if it isn't a boost crank, find a 3x crank and use the large ring position to move the chainline out. Direct mount rings for a mountain bike standard (boost chainline) may be hard to find. A higher Q-factor is better as it will keep the tip of the crank arm away from the chainstays. Finding a crank that has a road bolt pattern or has a spider to fit a CX / road ring would be best. There are some 40t rings for 104bcd out there but they aren't as common.

5. That will depend on the BB you use. Will there be enough space inside the shell for your cables?

6. BSA 73 is the most common mtb standard. It's extremely easy to use and to source parts for. T47 is gaining traction but isn't there yet. T47 is just a threaded PF30 shell. It helps with any creaking that a PF type can cause. They now make PF30 bb's where the two halves are threaded together to help with creaking as well. I'd decide on which crank you're going to use then get the appropriate BB shell. Otherwise, just get a BSA at 73mm wide.

[em_reeze]

Thanks for the answers guys. I emailed them yesterday so we will see what happens. I think I will go with BSA 73 mm bottom bracket. I might just have the dropper post internally routed down the seat tube and come out down there and then just have guides up the down tube. I am fine with the rest being externally routed. I still need to find a crank that works. I am wondering if I really need a 40T up front or if I should be going down to a 38T possibly. I am excited to see what they are able to come up with with my specifications!

[bxcc]

I think you’re on the right track. Internal routing is nice but external is just simpler. Just make sure the guides are in a spot that will allow for clean runs.

Check out their Alibaba store. That will give you some ideas of what they can do. I got most of my ideas from their other builds and put them together.
https://waltly.m.en.alibaba.com/

[em_reeze]

Does anyone know what grade titanium Waltly uses for the frames? It wasn't listed on my drawing and I never thought to ask. What are the pros/cons for the types? I haven't seen pictures of my frame yet but I am anticipating them any day now. I said ok to my final drawing on July 6, 2020 just for reference.

[tripleDot]

They used 3Al-2.5V titanium alloy. That's 3% aluminum, 2.5% vanadium mixed into the titanium. You can check it at their official website, http://www.waltlytitanium.com/.

As per my research (back then), for bicycle application, you can either use the 3Al-2.5V (most common), 6Al-4V or combination of both. 6Al-4V is lighter and stiffer than the 3Al-2.5V but more expensive.

[tripleDot]

Here's something I came across regarding Grade 5 (6Al-4V) vs Grade 9 (3Al-2.5V) titaniums.

https://www.ulbrich.com/blog/choosing-the-right-titanium-alloy-for-the-job-grade-9-vs-grade-5-titanium-comparison/

[em_reeze]

My frame arrived after 67 days. I placed the order on 7/7/2020 and it arrived in Colorado on 9/7/2020. The frame was packaged just fine and it did include a seat post clamp and a rear through axle. I did have to take it into a local shop so they could run the tap through the bottom bracket again as I don't own one of those taps and there was a burr that was hanging up installing the bottom bracket when I went to put it in. If I order another frame I will ask them to make sure that they run the bb tap through once before they ship it off. I was really impressed otherwise and love the frame. I put all my parts on and have been riding it around a lot up until yesterday when we got a foot of snow. The frame was 1971g without anything on it. The built up bike is around 22-23lbs with pedals. I have a 12 speed xt drivetrain with a 36T front chainring. The brakes are xt two pistons. I love the salsa bend 2 bars with 23 degree backsweep. My town commuter has surly terminal bars and I really like those also.

Fork: salsa firestarter 110 deluxe
Wheels: BTLOS WM-i24A
stem: whisky no 7 60mm
brakes: shimano xt 8100
cane creek hellbender 70 headset
WTB resolute tire front and back 42c
SDG duster seat
SDG tellis dropper post 170mm

Here are a few photos and the drawings from Waltly. I would buy another frame from them in the future. I think this one was $850 plus shipping and fees. I did draw this frame up in bikecad before I sent it off to Waltly to try and figure out the dimensions. I almost came up with the same dimensions as they did which is nice. There isn't much I would change if I was to make this same bike again. I forgot to route the derailleur cable on the left side by the headtube. I would also maybe just make the seat tube straight. Pretty minor changes.

[em_reeze]

A couple more photos and drawings.

[WindChaser8000]

Very nice build.  Thank you for posting your story, it is extremely helpful.

How are the wheels?

Would you buy from BTLOS again?

[em_reeze]

Thanks. I really like the bike. I only have 150 miles on the bike so far but the BTLOS wheels seem great. I would definitely buy from them again. I thought their website was easy to use and the options are nice. There are a couple different places that had similar looking product and prices I read a lot about them and decided on BTLOS.

[tripleDot]

Congratulations with that beauty!

[em_reeze]

I wanted to add a homemade chainstay protector to my Waltly ti gravel bike. I bought some Scotch Rubber Mastic Tape 2228 that is 1" wide for $10 or so. I think there is 10 feet of tape on the roll. I wanted to make the chainstay protector have some ridges to help dampen the chain slap when I ride on chunky trails. I am pretty happy with the result so far but we will see how long it stays on. I did use a heat gun on low to adhere it to the metal. I also cleaned the bike with a little rubbing alcohol before I applied the tape. What have you guys done for chainstay protection on similar bikes that don't already have one built in?

[tripleDot]

I used one of those $1.00 plastic chainstay protector on one bike. On another bike, I use the 3M Anti-Slip bathroom tape. Also used the same tape as my down tube protector.