1999 GMC Sierra 1500 Extended Cab Bolt Pattern
Checking fitment for your vehicle? Below you will find the factory bolt pattern (also known as the lug pattern) for the 1999 GMC Sierra 1500 Extended Cab, along with offset and center bore data.
| Bolt Pattern (Lug Pattern) | 6x139.7 (6x5.5") |
|---|---|
| Lug Nut / Bolt Size | 14x1.5 |
| Center Bore (CB) | 78.1 mm |
| Offset (ET) | 20-30 |
| Torque Specs | 100 ft-lbs (135 Nm) |
1999 Sierra 1500 Extended Cab — Year-Specific Fitment Context
The 1999 model year marks the beginning of the GMC Sierra 1500 Extended Cab's 6x139.7 bolt pattern era, which continued through 2013 (15 consecutive years). Wheels from any 1999–2013 GMC Sierra 1500 Extended Cab are cross-compatible with the 1999 model.
GMC Sierra 1500 Extended Cab Bolt Pattern by Year
The table below shows how the Sierra 1500 Extended Cab's wheel specifications have changed over the years. The 1999 model year is highlighted.
| Year | Bolt Pattern | Center Bore | Offset |
|---|---|---|---|
| ▸ 1999 | 6x139.7 | 78.1 | 20-30 |
| 2000 | 6x139.7 | 78.1 | 20-30 |
| 2001 | 6x139.7 | 78.1 | 20-30 |
| 2002 | 6x139.7 | 78.1 | 20-30 |
| 2003 | 6x139.7 | 78.1 | 20-30 |
| 2004 | 6x139.7 | 78.1 | 20-30 |
| 2005 | 6x139.7 | 78.1 | 20-30 |
| 2006 | 6x139.7 | 78.1 | 20-30 |
| 2007 | 6x139.7 | 78.1 | 20-30 |
| 2008 | 6x139.7 | 78.1 | 20-30 |
| 2009 | 6x139.7 | 78.1 | 20-30 |
| 2010 | 6x139.7 | 78.1 | 20-30 |
| 2011 | 6x139.7 | 78.1 | 20-30 |
| 2012 | 6x139.7 | 78.1 | 20-30 |
| 2013 | 6x139.7 | 78.1 | 20-30 |
Fitment Notes
The 1999 GMC Sierra 1500 Extended Cab has a bolt pattern of 6x139.7.
Imperial Conversion: This bolt pattern is commonly referred to as 6x5.5" in imperial units. When searching for aftermarket wheels, you may see them listed as 6x5.5".
This means it is a 6 lug pattern with a circle diameter of 139.7mm. When shopping for aftermarket wheels, ensure the "lug pattern" or "PCD" matches these numbers.
Year-to-Year Fitment Context
In our dataset, GMC Sierra 1500 Extended Cab appears from 1999 to 2013 (15 model years).
Across recorded model years, this model generally keeps the same bolt pattern.
- Observed bolt-pattern variants for this model: 1
- Observed center-bore variants for this model: 1
- Observed lug-size variants for this model: 1
- Observed total offset span across years: 50.0 mm
6x139.7 Pattern Context
This bolt pattern appears on 1067 vehicles in our current database and is considered common.
Examples of other vehicles using 6x139.7:
1999 GMC Sierra 1500 Extended Cab — Frequently Asked Questions
What is the bolt pattern for a 1999 GMC Sierra 1500 Extended Cab?
The 1999 GMC Sierra 1500 Extended Cab uses a 6x139.7 bolt pattern (also called lug pattern or PCD). The center bore is 78.1mm and the offset is 20-30mm.
What other years of GMC Sierra 1500 Extended Cab have the same bolt pattern as the 1999?
The GMC Sierra 1500 Extended Cab uses the 6x139.7 pattern from 1999 through 2013. Wheels from any of these model years are dimensionally compatible with the 1999, provided the offset and center bore also match.
How do I measure the bolt pattern on my 1999 GMC?
The 1999 Sierra 1500 Extended Cab uses a 6x139.7 pattern. For 4, 6, or 8-lug wheels, measure center-to-center across opposite holes. For 5-lug, measure from the center of one hole to the back of the opposite hole.
Can I put aftermarket wheels on my 1999 GMC Sierra 1500 Extended Cab?
Absolutely. Just ensure the aftermarket wheels have a 6x139.7 bolt pattern, an offset near 20-30mm, and a center bore of at least 78.1mm (using hub rings if larger).
Will wheels from another GMC fit my 1999 Sierra 1500 Extended Cab?
Only if they share the exact same 6x139.7 bolt pattern, a compatible offset, and a center bore equal to or larger than 78.1mm.
Can I use spacers on my 1999 GMC Sierra 1500 Extended Cab?
Yes, but ensure the wheel spacers match the 6x139.7 bolt pattern and 78.1mm center bore. Also verify that you have enough thread engagement for your 14x1.5 hardware.
Fitment Checklist Before You Buy Wheels
- This fitment uses a wide offset range. Check brake clearance and fender clearance before buying wheels.
- Torque lugs in a star pattern to 100 ft-lbs (135 Nm), then re-check torque after 50-100 km (30-60 miles).
Editorial Fitment Notes
GMC Sierra 1500 Extended Cab is generally consistent in bolt-pattern records across model years, but offset and hardware should still be validated before purchase.
- Observed production years in our database: 1999-2013 (15 model years).
- Observed bolt-pattern variants: 1 (6x139.7).
- Observed total offset span across years: 50.0 mm.
- Observed center-bore variants: 1 | lug-size variants: 1.
Data Quality & Review
Source note: Compiled from manufacturer fitment references, historical wheel data, and internal normalization rules.
Last reviewed: 2026-05-26 | Reviewed by: Bolt Pattern HQ Editorial Team
If you find a discrepancy for 1999 GMC Sierra 1500 Extended Cab, please report it via our About page contact so we can verify and update this record.