kevinf1990

Hi All, I have recently made the decision that I want to attempt a bike build from scratch. I believe I can do it and I hope this can be a learning process so please excuse any stupid questions.

I just got a Giant TCR frame. I have heard about people "facing" their frames. From what I understood, this means trying to eliminate any imperfections on the frame so that the bottom bracket or headset can sit flush to the frame. Is this still something that is necessary for carbon frames?

Regarding steerer tube cutting, I understand I need to measure how much I need to cut and add 3mm to the measurement to cut so that the stem will sit a little higher then the steerer tube. Is this correct? What is the best way to determine how much to cut when I don't have other parts in yet such as wheels, so I am not able to get on the bike to get a feel of the positioning.

The frameset came with some grommets and hardware. Most of them, I know where they go, but there were some grommets that I wasn't so sure of. What is the best way to figure out where they go? I understand that framsets don't really come with manuals since the manufacture most likely assumes that the person buying knows how to build a bike.

Again sorry for the noobie questions. I hope to learn as much as possible without breaking anything.

Homebrew01

Don't cut the steerer tube until you have ridden it for a bit, and are SURE of where you want the stem.
If it's ridiculously long, you could trim some off, but be sure to leave enough for adjustment as you get it fit for you.

When you do cut it, you can still leave a bit extra above the stem as "insurance" in case you want to raise it a bit a year from now.

superdex

First of all, welcome to a really enjoyable part of the hobby

I've built a number of bikes, and I've never faced anything. I wouldn't worry about it.

Leave the steerer length to the very end. You'll need to make sure you have enough steerer for the spacers you want, plus the stem, and then add your 3mm so you can have a 5mm spacer on top, then the topcap.

If it's a new frame, those grommets are to plug holes if you're going to run wireless electric shifting, or the like. Once you get cables run, you'll see where they need to go/not go.

And google/youtube/bikeforums should get you through it all safely. If you haven't bought a torque wrench, do that before you tighten anything. Something like https://www.chainreactioncycles.com/us/en/x-tools-essential-torque-wrench-set/rp-prod155414 will work great, but to get the right torque on bottom bracket cups and cassette you should grab one like this too: https://www.harborfreight.com/hand-t...nch-63880.html

With carbon, respect the torque settings.

Unca_Sam

You're right about facing, though I understood it to be more about removing paint and correcting manufacturing tolerances to ensure that both faces are in fact parallel. The issue is that when the cups in the head tube or bottom bracket aren't parallel, the bearings are unnecessarily stressed and will wear unevenly.

The good news is that your LBS is likely to be able to do it, and can tell you if it's necessary on your frame! It's a relatively quick job with the right tool, so it's not usually expensive, especially if they don't need to remove the headset races and BB first.

So it's not too expensive to contract out, and it can extend the life of any bearings you're using in the bike. I've only ever rebuilt frames, so I just stick with the headset and the BB face is usually paint free already.

Andrew R Stewart 

Facing "needs" depends on the design of the bearing seating with the frame. As example if the BB shell uses press fit bearings that are held by the shell's ID and located by an internal shoulder/seat the facing the shell's face will do nothing to effect the bearing, for better or worse. But if the shell is a threaded design where the bearing "cup" is tightened against the shell's face then, yes, insuring the bearing seats square to the shell's axis is important. So to with headsets. Bearings that seat within the HT's ID (like an integral style often does) has no association with the HT's faces. But cups that press against the face/ends of the HT do benefit from facing.

Giant TCRs have had a few differing designs over the years. Which do you have, WRT the bearing designs? Andy (as always wondering about the details not mentioned by the OP)

cpach

If it's a semirecent TCR you shouldn't really need to do any frame prep. The HS bearings sit directly into the molded frame, and the BB should be to tolerance for PF86 from the factory.

kevinf1990

This is the frame that I got (https://www.giant-bicycles.com/us/tc...-frameset-2020). I do have a torque wrench for when I worked on cars, it is also able to go to lower torques such as 5nm. I think I would use this bottom bracket (this)? It came with a compression plug


This is the first time I've seen this. I guess the videos that I see on youtube were mostly aluminum steerers which uses a star nut. I think I just drop this into the steerer and tighten the bolt on the top? The outside is a "sandy" texture, would I still need to put any friction type paste on it?

cpach

That's a sweet frameset. Yeah, that's the right BB. I'd recommend having the correct sized drift for installing the BB. Assembly paste isn't a bad idea for the expander but also probably not strictly necessary. Think about how the expander will support the steerer with the stem clamps installed, while also having it low enough that you can appropriately preload the headset.

The frame probably comes with multiple frame grommets to accommodate 1x, di2, etc.

The one thing you MAY need faced is the flat mounts on the frame/fork. I've seen a sizable minority of current production Giant bikes that benefit from facing these. Basically if when you install the brake it seems vertically canted and you can't get a quiet brake adjustment the mounts probably need to be faced, which a good high volume shop should SHOULD have.

Kapusta

I leave my steerer tubes pretty long at first. Like, 25mm past the stem with three 10mm spacers. Then I move spacers to/from above to below the stem to get the fit where I know I want it. A bar swap, rotating the bars, or changing where the hoods sit can all have some effect on where the stem ends up.

Once I feel pretty comfortable I know what my setup is, I cut the steerer about 7-8mm over the stem and run a 10mm spacer in top.

HillRider

As noted, make cutting the steerer to the final length the last thing you do. Ride with a too long steerer and spacers above the stem until you are sure where you want the bars.

Conventionally, when you do cut the steerer, you subtract 3 mm from the measured length to assure the steerer is slightly below the top of the stem to leave clearance for headset adjustment. However, I seriously recommend you leave the steerer 3 or more mm too LONG so it projects above the stem and add a spacer above the stem to achieve the needed adjustment gap. That assures the stem is fully supported by the steerer and leaves room for a bit of adjustment if you want to raise the bars later. I leave my steerers about 7 mm too long and use a 10 mm spacer above the stem.

Litespud

First-off - good for you for taking this on - if you're any way mechanically inclined, it's pretty straightforward and very satisfying.
A couple of things - a torque wrench for most automotive applications will have quite a high range (mine are, for example, 20-100 ftlb and 50-250 ftlb, or something like that). 5Nm is likely at the very bottom of the range, and torque wrenches and to be inaccurate at range extremes. I personally wouldn't use an automotive wrench for a 5 Nm application, like installing stems or bars - get yourself an inexpensive beam wrench in a range more appropriate for the purpose - something like, maybe 2-10 Nm.
You're not going to be able to gauge how much to cut the steerer until the bike is near-complete - at least until you can sit on it. Once you're at that stage, position the stem with as many spacers underneath as necessary to achieve the required height. Then mark the steerer maybe 1" higher than the stem and cut. I use a cheap threadless stem as a guide for a nice perpendicular cut. If cutting a carbon steerer, many recommend a specialized hacksaw blade - I have always used a new standard blade, putting relatively little pressure on it, so the blade does the cutting - you want to cut through the CF fibers, not rip them apart. I keep everything wetted down with a hose to keep CF dust down. I also cut outside. I finish off the cut edge with some wet sandpaper. This approach has always worked for me. Once the stem is cut, you'll need to add further spacers that extend ~3 mm higher than the cut steerer. If a CF steerer, you'll need to position the expander plug so that it is located inside the steerer level with the stem on the outside, to support the steerer against the stem clamp pressure on the outside. Depending on how much steerer you left above the stem, this might necessitate a longer stem cap screw. Your LBS should have a bunch of these in their spares boxes. Once the stem is installed and you start riding, you can fine-tune the stem height, shifting spacers from below to on top and vice-versa, as necessary. Take you time to get it right. The last time I installed a fork, I rode the bike for a year before I finally committed to a "perfect" stem height, finally trimmed the steerer and did away with the upper spacers (I don't like the look of the steerer sticking up above the stem)

kevinf1990

Regarding steerer tube, I can measure from the bottom of the steerer tube to where I want to cut and subtract 3mm (meaning removing more steerer tube). If I go with this route, my stem would be sitting at the top with no spacers above the stems.

The other way would be to measure from the bottom of the steerer tube to where I want to cut and add 3mm (meaning removing less steerer tube then I need). If I go with this route, then I would put in my spacers, then stem, then maybe a 3mm spacer above the stem and then stem cap?

Also what are good torque wrenches that are affordable (i.e cheaper then the Park tools TW-5.2) for bicycle applications?

Litespud

Leave more than 3mm above the stem at this point - until you've ridden the bike, with the bars and brifters in the desired positions, it's going to be hard to fine-tune your stem position - you want to leave yourself as much room for adjustment as possible. I don't know what you mean by measuring the steerer from the bottom of the steerer tube - IMO this isn't a great way to determine the cut point - just get the stem into the approximate position, with the requisite (if any) spacers underneath, mark the position of the stem top on your steerer, and base everything off that mark - cut 3mm lower than that mark if you know your stem is in the ideal position (although I don't know how you could make that determination if you haven't ridden the bike), or cut ~1" higher than that mark if you haven't spent any time on the bike identifying the ideal stem height.
I've been pretty happy with Kobalt 1/2" and 3/8" click wrenches from Lowes - well made and seemingly pretty consistent, but the trick with torque wrenches is to baby them a little - don't knock them around, de-tension them when not in use, and keep them in their cases. On the bike, I use the 3/8" for installing the BB, crank and cassette. For low-torque applications (pretty much everything else), I have a 3/8" click-type (brand u/k) graduated in inlb, but the range was a little high for CF component applications, so I went with a beam-type 1/4" wrench I found on Amazon - can't remember the brand, but it cost ~$20. There's not a lot that can go wrong with a beam-type. Park stuff is OK, but IMO you pay a lot for what you get (it's that "blue surcharge"). Unless it's an exclusively bike tool (i.e., with no other application), I usually look elsewhere. $108 for a low range torque wrench seems like a lot (although that might be just Competitive Cyclist pricing - they're not the cheapest, and you might find the same wrench elsewhere for less). My 50-250 ftlb Kobalt, which is well made and has been great, cost ~$90.

squirtdad

it will make you build much easier if you get matching parts, especially for the first build what component group are are you thinking? you will need to match the BB to the crankset you use

UK online shops used to have great deals but that is going away (ultegrat $800 one left https://www.ribblecycles.co.uk/shima...uble-groupset/)

it is almost always more expensive to build you own (unless you have a large stash of parts) than to buy a complete bike.......that is info, not meant to deter you from the path

ljsense

Don't cut your steerer tube at all for now. It's not something you want to calculate -- you want to see and feel exactly where the cut should be after everything has been installed.

Others have given you good advice, I just want to try to amplify.

Get a stack of steer tube spacers and build up the entire bike. Use the spacers to fill the distance between the headset, stem, and top cap. You can then move the stem up and down among the spacers to see exactly where you want it. Ride it. Experiment. Do not cut anything.

When you're sure you have the handlebars where you want them, get ready to cut. Take off the top cap and any spacers under it. Scribe a line with a pencil, a white paint marker or something similar using the top of your stem as a guide. Take off the stem, remove the fork and then decide if you want to be conservative and cut above the line by 3 mm and use a spacer, or a bit below it and go without. Your top cap determines how much below the stem you need to cut. 2-3 mm usually does it.

If you use a clamp to hold your steer tube when you cut it, don't crush it. Don't clamp it down like it's a 2x4 or something.

WizardOfBoz

Facing is a machining term that would mean cutting metal off a surface to get a flat and perpendicular face. One way to build a metal frame is to cut the bottom bracket to exact width and the headset to exact length, put them in a fixture that holds the frame tubes (and lugs if you are brazing) together and weld or braze. Then hope that the tubes didn't distort and that the paint went on evenly. Normally the tubes would be fine and this was the common method of mfr. for old vintage frames. But if the tubes were sloppily cut (not at a right angle) or were distorted in welding, or if you had big honking paint drips, then you'd have an issue. To solve this, you would face the BB or head tube. This involves proper fixturing and metal cutting tools. The end result would allow your BB or headset bearing cups to be installed perfectly perpendicular to the relevant tube. Some bikes were actually welded up and then were sent out with imperfect tubes - the ends were at an angle. So one can take measures to refurb such bikes by facing. It's not too commonly done a thing. The bikes good enough to be worthy of the effort tended not to have muffed up tube facing. And the frames with muffed up tube facing often weren't those inspiring the owners to drop a lot of dough on fixing the bike up. Plus, owners of such bikes rarely would recognize the issue. (Generally - there are exceptions).

CF frames should be set up when they are made so that everything is perpendicular, straight, and plumb. Also, there is often not a lot of extra CF matrix to face off. Others may have different opinions, but I'd suspect that you don't need to face anything on the CF frame.

As others above have indicated above, make sure you have the stem length set up so that you like the way the bike rides. Then have an LBS cut the fork using a saw guide. This ensures a perpendicular cut - you shouldn't need to face the top of the steerer tube if the cut is done right.

ljsense

I thought this was a great answer about how facing came about, and why people still talk about it.

It's definitely not needed with your frame, both for what WizBoz laid out, and for what others pointed out about how the headset and bottom bracket bearings are placed.

As for the grommets, you probably have ring shaped one where the rear derailleur housing leaves the frame near the dropout.

Another covers a battery port, probably. Your cables and cable housing may pass through them.

My best advice would be to contact Giant. They don't distribute assembly manuals, but if they are like Trek and other big manufacturers, they have wonderfully detailed specs and build sheets for shops and assemblers to show how it's all supposed to go together.

If you have no luck with them, I'd go to a shop that has Giant TCRs built and ready to sell and look at the bike in person to get a good handle on where the various fittings are placed.

kevinf1990

I am about to buy some of the first parts for the bike (trying to do this build slow and take my time). What tool would I use to press the bottom bracket into the carbon shell? I have seen many different tools but would like to get one that is not too expensive but will get the job done. I assume the bottom bracket is supposed to be pressed into the frame dry or do I need any kind of paste?

Also, I am planning to run a 34/50 in the front and 11/32 in the back, I think I would need a medium cage rear derailleur right?

cpach

Two of these: https://www.amazon.com/Wheels-Manufa...s%2C199&sr=8-1 plus some threaded rod, or if you don't want to DIY the rod, just get the kit https://www.amazon.com/TOOL-BEARING-...s%2C199&sr=8-5.

Use a little bit of grease when pressing in. If the press fit is loose or you develop problems with creaking, you can also use a bearing retaining compound like Loctite 609.

Medium cage (GS) der for that combo.

DaveSSS 

I've been building bikes since the 80's. Never found a frame that needed facing. A good shop would tell you that modern CF frames shouldn't need it.

Phil_gretz

I'd echo what others have said about accurate torque values. Get two torque wrenches, one for high end (bottom bracket bearing) and one for low end (seatpost clamp) values. The click type (when tested) often show good values relative to standards, but sometimes they don't. I prefer the beam type, and these can be found pretty inexpensively on Craigslist. Don't guess, measure your bolt torques as you build.

kevinf1990

What do you guys think about this one? https://www.amazon.com/gp/huc/view.h...daf2c44b1a%2C1